After successfully loading the HSMM firmware on the WRT54G v2 and v4 I bought off eBay, I moved on to a WRT54GL v1.1 I was given.   The other two had the stock Linksys GUI and were no problem, the GL has DD-WRT v24-sp2 (07/21/09) vpn.  After a 30-30-30 and changing the UN and PW to be able to get to Administration -> Firmware Upgrade and browsing to the .bin, my browser (Firefox 21) will give me a "Connection  Reset" page after about a second.  I can remove the /upgrade.cgi from the url (or close the page and enter 192.168.1.1 in a new one) and I'm back at the DD-WRT Control Panel/System Information.  I've tried installing the HSMM and Linksys .bin for the correct model/version using the DD-WRT interface with the same result.

I found these directions   http://infodepot.wikia.com/wiki/Linksys_WRT54GL_v1.1   and using the current Linksys firmware (since the one there is a dead link) but if a static ip and power-cycling is supposed to get me a Linksys web gui and not the DD-WRT page wanting me to change the default UN & PW, it's not happening.

Any guidance before I wear out the AC outlet unplugging and plugging the wall-wart?  Thanks!

Shouldn't be an issue.  Not sure what the deal was with the one I had, I spent at least an hour of rebooting and logging in trying to get it to accept the firmware upgrade, had just about given up and one of the guys from the IT department walked in, clicked on "Administration" and off it went.  Ever have one of those days?

A couple of additional hints:

1) Sometimes, windows is batstuff crazy in the way it handles network interfaces, especially once it's connected and the IP address changes.  Sometimes you have to power off of the PC, or at least a reboot is needed.  What's particularly infuriating is that it may work right 10 times in a row, and then completely fail the 11th time you try the same thing. 

2) Sometimes the WRT-54s get screwy when flashing and you need to unplug the power overnight. 

I am a longtime DD-WRT user on Linksys routers, primarily the WRT54X* series... first off, the best place to initiate the power cycling for a full reset is the router end of the power cord, not the wall end... it's a quicker power off and on for the router...

as for the issue with Firefox? I have had that as well, FF can be kinda flaky at times, but usually closing it, waiting 30 seconds gets it, if not try (YUCK!) I.E.... also, you may and often do have to disable your computer's firewall temporarily... (I know I sure have) also be sure you change to the new network if needed while it is rebooting and making changes (I've missed that one a few times myself)

lastly? check the router you have... make sure that if you are trying to change the firmware to a different type, like from DD-WRT to Tomato, or OPEN-WRT, that you are aware of the flash and ram sizes... some versions of the router really need for you to go to the "Mini" or "Micro" versions so that there is room in the flash to load the new firmware... if not, they will fail every time, and sometimes brick... (mainly the ones with 4MBFlash, 8MB RAM) I tend to try to stick with the ones with 8/32 and use the Mega builds...

Seannon KD4IYI