I have seen the other posts on this topic. I have not seen a solution or even an acknowledgment that there is a problem. So here is what I see.
Running XP. No software firewall. Avast 4.8-1229. Occasionally, two or three times a week, all browsers stop receiving internet data, in both Firefox and IE. In firefox it gets stuck at "waiting for http:.........."). This also tells me in is getting past sending to the DNS server. So only inbound TCP/IP data is blocked. I cannot even see my router, 192.168.1.1. All other internet operations, in and out, are not effected. Email, P2P, pinging, etc are OK. If I disable Web Shield (or reboot), it is fixed. I also run Spyware Terminator, but I disabled it, and soon enough it happened again. And, just for fun I installed Avast on another computer that had been running AVG. It took several days, but it did it too.
There is a very real problem here, although it is not constant and I guess does not happen on all systems. Sure looks like it is blocking Port 80 inbound. Right now I am just running with Web Shield turned off. After reading what it does I don't think it is very useful anyway. But, I do like to solve problems. Any ideas as to which way to pursue this? (I am a SW engr).