Thanks for the great tips. Between these, and some help from other sites, I was able to get my WRT54GS working again. (Bought off ebay, seller had flashed openwrt on it but screwed it up...)
I was having trouble getting anything to flash, and TFTP wasn't working for me either... But I finally got it to work fairly reliably by doing the following:
1) Set my network adapter speed/duplex to 10 MBbps, half-duplex.
2) Unplug router power & any ethernet cords.
3) Plug ethernet wire from computer to LAN port 1.
4) Open command prompt window, type the TFTP command, but don't hit enter yet.
5) Plug power cord in for the router, watch the lights carefully.
6) As soon as the LED for LAN port 1 lights up, hit Enter in the command prompt window.
I had no trouble with TFTP working when I did those steps. A couple minutes later, I could bring up the web interface for the router!
Note that this procedure worked for both the Linksys firmware and the dd-wrt firmware...
Enjoy!
Message Edited by A_Generic_User on 09-16-2008 04:22 PM