the same story with my tp a couple of months ago. i guess it's all about the firewall settings. anyway it's my opinion. what i did was reinstalling win7 and make an internet sharing connection on a "clean" wndows 7. you got the connection? ok. now make a FULL backup of your clean win7 and then only install your antivirus and firewall apps. it helped me.
if it seems pretty boring to go thru it all then you'd better dig into your firewall settings - that is the problem
