If you own a Linksys WRT54G3G and you are having problems then please keep reading. I have worked for a couple of months now to figure out why my router and my Pantech PX-500 card would not work properly together. I was already running Linksys 2.00.9 firmware and my Pantech card also had the most recent firmware. My router would not stay connected, would not auto connect all the time, and just overall was very unreliable. After upgrading my router with OpenWRT Firmware I was able to finally have a reliable internet connection.
Please see this thread below for information on where to find the OpenWRT firmware and how to install the new firmware on your router.

OpenWRT Firmware for WRT54G3G- New Aug. 25th : EVDOforums.com

Update: 12/16/2008
If you are looking to purchase one of these great routers I would check eBay. I just purchased one shipped for under $60