He encontrado esto:

Q:

Every time I attempt to execute arpspoof I get the following error: arpspoof: couldn't arp for host 10.1.1.1. I have tried various command line switches and nothing appears to work.

A;

I received this error on my Slackware 11 installation which was compiled from source as opposed to using a package manager. The function arp_cache_lookup does not use the correct interface when running under Linux .. it always uses interface "eth0".. Don't fret, we can change this without too much effort. Change directory to where you unpacked dsniff to, you will want to find the file arp.c and edit a single parameter within it. Using your favorite editor open arp.c and change the following:

strncpy(ar.arp_dev, "eth0", sizeof(ar.arp_dev));

to

strncpy(ar.arp_dev, "wlan0", sizeof(ar.arp_dev));

Save the file and recompile the application.

If you have other issues, you got it running properly or you just want to drop a line feel free to leave a comment.

May Your Skill Prevail.

Fuente: http://blog.ironguard.net/2007/06/how-to-use-webspy-from-dsniff-suite.html

Pero no tengo ni una minima idea de como aplicarlo, ya que no encuentro ese supuesto archivo arp.c

Decir que estoy utilizando wifiway 2 en un usb.

La pregunta por si me he enrollado mucho es:

¿A alguien mas le pasa o es solo a mi?

Si solo es a mi. ¿Por que puede ser??

Soy novato profundo.  Saludos y Gracias !