It is a WRT54G v4 running the most recent version of Tomato.
I'd be willing to bet that Tomato is causing some of your issues. I used it for the last few years without ever having any problems. Updated from v19 to v23 and it seemed like I had problems non-stop. Tried going down to v22, still had issues.
Just for sh!ts and giggles, I switched to DD-WRT and all my issues have vanished.
Unless one is a glutton for punishment, I don't know how anyone can do proper troubleshooting unless they strip down to the core and work from there. Otherwise you are beating your head against the wall.