Ok this has been happening to me for about 3 years now , it has just gotten to the point where I am not going to give up until I find a solution. I used to think it was just the mobo on my old pc , yet I just built a new rig a few months ago and its still doing it.

The exact problem: When I connect my xbox to computer to ftp files back and forth my wireless connection on the pc will slow down and eventually drop?

If anyone knows what is causing this , has any solutions it would be greatly appreciated!!

make sure your wireless router has an up to date firmware.

make sure the drivers for your wireless card are up to date.

try a different wireless card or wireless router if that doesnt fix it.

if all 3 of those dont fix it, ... try a hardwired setup just to verify it is indeed a wireless problem.

if the above 4 dont fix it, i dunno, pick your favorite blunt weapon and beat it till it breaks or starts working properly.

Same issue here (only without the x-box). Two of us seem to be the only ones?
Postet to ubuntu forum as well (http://ubuntuforums.org/showthread.php?t=874700)