HAHA:)) Lavamike, i had something like you, i instaled the best firewall in this year and a Nod32 last version and they was blocking my connection, it was like i was with a bit per second and(better without internet),And when i reformated my pc i instaled them again,the same problem,i uninstalled the anti virus and the firewall,internet works:D
So,this anti viruses and firewalls are ...some bull shits;)(to find out why my internet dont works i reformated my pc 3-4 times in a day)