AH HA!!!
Ditch AVG. I bet that is where the root of your problem lies.
I used AVG for a few weeks and it consistently fucked with my internet connection, causing nasty drop-outs and all sorts of things. I bet you a dollar that is the problem.
I had the same problem, thought it was my modem, had Comcast give me a new one, still didn't fix it, bought a new router, no go. Removed AVG and VOILA! no problems since the day I removed it.