I have been running into an issue similar to this. I am running the new 1.22b05 however, I updated to this to try and fix the issue, but still seems to be running into this. I think I hit this issue when going from 1.11 to 1.2+.
My symptoms are:
Internet will slow down. Wireless will be "connected", but I can't login to the router. Wired has the same issue. Internet completely stops. If I go to the modem, its activity light is solid orange, doesn't even get a break from data. When I unplug/plug in the router, the internet returns to normal and it works for a couple days and then I run into the same issue. Its been so annoying that I am thinking about getting a new router, but have been waiting for 1.22/1.3 final.
If this isn't what you are seeing, sorry for posting this, I will make a new thread.