Network card crash when downloading

[My Yute]

I'm having a problem where under heavy network usage (bittorrent downloads, software updates) my airport card crashes. Basically I can't see any network in my area and turning off and on the airport in no way alleviates this problem. I've gotten my ibook replaced, my RAM replaced and I'm still having this problem. When this problem occurrs my root_kernal task also takes a lot of CPU cycles which makes my mouse very jumpy. I've found two other people on this board with the same problem and it seems what we have in common is installing 1 gig of RAM (theirs from crucial, mine from data memory systems). We all have the latest revision ibook. I'm just putting this out there to see if anyone else is having this problem so we can hopefully see what our computers have in common (programmes being run, etc) and find a way to fix this problem. So anyone else experiencing this?