En serio crees que no actualice la pagina?  , no estan las manitos en Firefox. Silverlight 3.0, noscript desactivado, FF 3.5.5. En Chrome si andan.

Por cierto, te fijaste esta Silverlight.available? lamentablemente es de silverlight.js pero esta devuelve true si esta instalado (cualquier version)

Silverlight.isInstalled=function(b){if(b==undefined)b=null;var a=false,m=null;try{var i=null,j=false;if(window.ActiveXObject)try{i=new ActiveXObject("AgControl.AgControl");if(b===null)a=true;else if(i.IsVersionSupported(b))a=true;i=null}catch(l){j=true}else j=true;if(j){var k=navigator.plugins["Silverlight Plug-In"];if(k)if(b===null)a=true;else{var h=k.description;if(h==="1.0.30226.2")h="2.0.30226.2";var c=h.split(".");while(c.length>3)c.pop();while(c.length<4)c.push(0);var e=b.split(".");while(e.length>4)e.pop();var d,g,f=0;do{d=parseInt(e[f]);g=parseInt(c[f]);f++}while(f<e.length&&d===g);if(d<=g&&!isNaN(d))a=true}}}catch(l){a=false}return a}

//v2.0.40818.0
if(!window.Silverlight)window.Silverlight={};Silverlight._silverlightCount=0;Silverlight.__onSilverlightInstalledCalled=false;Silverlight.fwlinkRoot="http://go2.microsoft.com/fwlink/?LinkID=";Silverlight.__installationEventFired=false;Silverlight.onGetSilverlight=null;Silverlight.onSilverlightInstalled=function(){window.location.reload(false)};Silverlight.isInstalled=function(b){if(b==undefined)b=null;var a=false,m=null;try{var i=null,j=false;if(window.ActiveXObject)try{i=new ActiveXObject("AgControl.AgControl");if(b===null)a=true;else if(i.IsVersionSupported(b))a=true;i=null}catch(l){j=true}else j=true;if(j){var k=navigator.plugins["Silverlight Plug-In"];if(k)if(b===null)a=true;else{var h=k.description;if(h==="1.0.30226.2")h="2.0.30226.2";var c=h.split(".");while(c.length>3)c.pop();while(c.length<4)c.push(0);var e=b.split(".");while(e.length>4)e.pop();var d,g,f=0;do{d=parseInt(e[f]);g=parseInt(c[f]);f++}while(f<e.length&&d===g);if(d<=g&&!isNaN(d))a=true}}}catch(l){a=false}return a};Silverlight.WaitForInstallCompletion=function(){if(!Silverlight.isBrowserRestartRequired&&Silverlight.onSilverlightInstalled){try{navigator.plugins.refresh()}catch(a){}if(Silverlight.isInstalled(null)&&!Silverlight.__onSilverlightInstalledCalled){Silverlight.onSilverlightInstalled();Silverlight.__onSilverlightInstalledCalled=true}else setTimeout(Silverlight.WaitForInstallCompletion,3e3)}};Silverlight.__startup=function(){navigator.plugins.refresh();Silverlight.isBrowserRestartRequired=Silverlight.isInstalled(null);if(!Silverlight.isBrowserRestartRequired){Silverlight.WaitForInstallCompletion();if(!Silverlight.__installationEventFired){Silverlight.onInstallRequired();Silverlight.__installationEventFired=true}}else if(window.navigator.mimeTypes){var b=navigator.mimeTypes["application/x-silverlight-2"],c=navigator.mimeTypes["application/x-silverlight-2-b2"],d=navigator.mimeTypes["application/x-silverlight-2-b1"],a=d;if(c)a=c;if(!b&&(d||c)){if(!Silverlight.__installationEventFired){Silverlight.onUpgradeRequired();Silverlight.__installationEventFired=true}}else if(b&&a)if(b.enabledPlugin&&a.enabledPlugin)if(b.enabledPlugin.description!=a.enabledPlugin.description)if(!Silverlight.__installationEventFired){Silverlight.onRestartRequired();Silverlight.__installationEventFired=true}}if(!Silverlight.disableAutoStartup)if(window.removeEventListener)window.removeEventListener("load",Silverlight.__startup,false);else window.detachEvent("onload",Silverlight.__startup)};if(!Silverlight.disableAutoStartup)if(window.addEventListener)window.addEventListener("load",Silverlight.__startup,false);else window.attachEvent("onload",Silverlight.__startup);Silverlight.createObject=function(m,f,e,k,l,h,j){var d={},a=k,c=l;d.version=a.version;a.source=m;d.alt=a.alt;if(h)a.initParams=h;if(a.isWindowless&&!a.windowless)a.windowless=a.isWindowless;if(a.framerate&&!a.maxFramerate)a.maxFramerate=a.framerate;if(e&&!a.id)a.id=e;delete a.ignoreBrowserVer;delete a.inplaceInstallPrompt;delete a.version;delete a.isWindowless;delete a.framerate;delete a.data;delete a.src;delete a.alt;if(Silverlight.isInstalled(d.version)){for(var b in c)if(c[b]){if(b=="onLoad"&&typeof c[b]=="function"&&c[b].length!=1){var i=c[b];c[b]=function(a){return i(document.getElementById(e),j,a)}}var g=Silverlight.__getHandlerName(c[b]);if(g!=null){a[b]=g;c[b]=null}else throw"typeof events."+b+" must be 'function' or 'string'";}slPluginHTML=Silverlight.buildHTML(a)}else slPluginHTML=Silverlight.buildPromptHTML(d);if(f)f.innerHTML=slPluginHTML;else return slPluginHTML};Silverlight.buildHTML=function(a){var b=[];b.push('<object type="application/x-silverlight" data="data:application/x-silverlight,"');if(a.id!=null)b.push(' id="'+Silverlight.HtmlAttributeEncode(a.id)+'"');if(a.width!=null)b.push(' width="'+a.width+'"');if(a.height!=null)b.push(' height="'+a.height+'"');b.push(" >");delete a.id;delete a.width;delete a.height;for(var c in a)if(a[c])b.push('<param name="'+Silverlight.HtmlAttributeEncode(c)+'" value="'+Silverlight.HtmlAttributeEncode(a[c])+'" />');b.push("</object>");return b.join("")};Silverlight.createObjectEx=function(b){var a=b,c=Silverlight.createObject(a.source,a.parentElement,a.id,a.properties,a.events,a.initParams,a.context);if(a.parentElement==null)return c};Silverlight.buildPromptHTML=function(b){var a="",d=Silverlight.fwlinkRoot,c=b.version;if(b.alt)a=b.alt;else{if(!c)c="";a="<a href='javascript:Silverlight.getSilverlight(\"{1}\");' style='text-decoration: none;'><img src='{2}' alt='Get Microsoft Silverlight' style='border-style: none'/></a>";a=a.replace("{1}",c);a=a.replace("{2}",d+"108181")}return a};Silverlight.getSilverlight=function(e){if(Silverlight.onGetSilverlight)Silverlight.onGetSilverlight();var b="",a=String(e).split(".");if(a.length>1){var c=parseInt(a[0]);if(isNaN(c)||c<2)b="1.0";else b=a[0]+"."+a[1]}var d="";if(b.match(/^\d+\056\d+$/))d="&v="+b;Silverlight.followFWLink("149156"+d)};Silverlight.followFWLink=function(a){top.location=Silverlight.fwlinkRoot+String(a)};Silverlight.HtmlAttributeEncode=function(c){var a,b="";if(c==null)return null;for(var d=0;d<c.length;d++){a=c.charCodeAt(d);if(a>96&&a<123||a>64&&a<91||a>43&&a<58&&a!=47||a==95)b=b+String.fromCharCode(a);else b=b+"&#38;#"+a+";"}return b};Silverlight.default_error_handler=function(e,b){var d,c=b.ErrorType;d=b.ErrorCode;var a="\nSilverlight error message     \n";a+="ErrorCode: "+d+"\n";a+="ErrorType: "+c+"       \n";a+="Message: "+b.ErrorMessage+"     \n";if(c=="ParserError"){a+="XamlFile: "+b.xamlFile+"     \n";a+="Line: "+b.lineNumber+"     \n";a+="Position: "+b.charPosition+"     \n"}else if(c=="RuntimeError"){if(b.lineNumber!=0){a+="Line: "+b.lineNumber+"     \n";a+="Position: "+b.charPosition+"     \n"}a+="MethodName: "+b.methodName+"     \n"}alert(a)};Silverlight.__cleanup=function(){for(var a=Silverlight._silverlightCount-1;a>=0;a--)window["__slEvent"+a]=null;Silverlight._silverlightCount=0;if(window.removeEventListener)window.removeEventListener("unload",Silverlight.__cleanup,false);else window.detachEvent("onunload",Silverlight.__cleanup)};Silverlight.__getHandlerName=function(b){var a="";if(typeof b=="string")a=b;else if(typeof b=="function"){if(Silverlight._silverlightCount==0)if(window.addEventListener)window.addEventListener("unload",Silverlight.__cleanup,false);else window.attachEvent("onunload",Silverlight.__cleanup);var c=Silverlight._silverlightCount++;a="__slEvent"+c;window[a]=b}else a=null;return a};Silverlight.onRequiredVersionAvailable=function(){};Silverlight.onRestartRequired=function(){};Silverlight.onUpgradeRequired=function(){};Silverlight.onInstallRequired=function(){};Silverlight.IsVersionAvailableOnError=function(d,a){var b=false;try{if(a.ErrorCode==8001&&!Silverlight.__installationEventFired){Silverlight.onUpgradeRequired();Silverlight.__installationEventFired=true}else if(a.ErrorCode==8002&&!Silverlight.__installationEventFired){Silverlight.onRestartRequired();Silverlight.__installationEventFired=true}else if(a.ErrorCode==5014||a.ErrorCode==2106){if(Silverlight.__verifySilverlight2UpgradeSuccess(a.getHost()))b=true}else b=true}catch(c){}return b};Silverlight.IsVersionAvailableOnLoad=function(b){var a=false;try{if(Silverlight.__verifySilverlight2UpgradeSuccess(b.getHost()))a=true}catch(c){}return a};Silverlight.__verifySilverlight2UpgradeSuccess=function(d){var c=false,b="3.0.40818",a=null;try{if(d.IsVersionSupported(b+".99")){a=Silverlight.onRequiredVersionAvailable;c=true}else if(d.IsVersionSupported(b+".0"))a=Silverlight.onRestartRequired;else a=Silverlight.onUpgradeRequired;if(a&&!Silverlight.__installationEventFired){a();Silverlight.__installationEventFired=true}}catch(e){}return c}