I used to use the WRT54G, and switched to an SRX400 based Linksys router. My WRT54G had the same issue yours did, but it didn't happen very often.
Some obvious things first: have you used the latest firmware? If anything, this may be of some help.
Is the router new? If so, you could try exchanging it for another, if you thought maybe that was the issue.
Less obvious ideas: The WRT54G is -very- hackable. Visit Sourceforge, and search for new firmware there. Non-Linksys created firmware -could- solve your problem. It even allows you to change the decibel levels your router puts out, effectivly giving you greater range off your device. Not sure if it would solve your issue, but it is worth a shot.
Finally, a last note, in case you have to live with this issue for awhile before you get it fixed - I have all my network based items on one power strip. Then, if I ever have connectivity issues, with the flip on a switch on the power strip, I can reset the modem, router, print server, and file server.