Also,
instead of just:

catch(UnknownHostException nohost){}


make a print out, to see if you are not getting into the catch
for example:

try{
YourAd = InetAddress.getLocalHost();
System.out.println(" -- YourAd has been set to: " +
toString().YourAd );
// or just + YourAd, I don't know InetAddress Class.
}

catch(UnknownHostException nohost){
System.out.println(" -- Error: YourAd has not been set! --
" );
}


return YourAd;
}
}

I would suspect that if it works on someone else's system, then
the object of ComputerName class  is being created, fine, but for some
reason the YourAd is not set. I think...
Good luck. Will be interested to know how you made out.