Folks
I also have a Linksys (although its the WRT54G). I had similar problems, until I flashed it with the DD-WRT firmware. My problems have disappeared and I also have improved features and functionality (one of the best is the ability to adjust the transmission power of the router. You'll find other posts discussing this on here, however for convenience have a look at these
http://www.dd-wrt.com/wiki/index.php...er_Information
http://www.wrtrouters.com/router/wrt54gs/
Hope this helps.
Cheers