I had this issue on Windows XP SP2 where my wireless connection kept dropping out every 20 secs or so. Somehow I managed to solve this problem by reading a article on this forum.
The guy managed to stop it by disabling "Wireless Zero Config" in the Windows XP Services dialog and which also worked for me!
However, I've recently made the move to Windows Vista, which i'm quite happy with up until I look at the pings. It appears my problem has popped up again. However, I can't find the equivilant of "Wireless Zero Config" on Windows Vista.
Anyone have any ideas what they could have renamed it to? Or even intergrated it into something else (I hope not!)