At this point I'm assuming you have it running as administrator like all the other threads have suggested? I probably should have asked that first. If you don't want to disable your antivirus/firewall, you'll have to wait till someone else comes along with a solution.
I'm running the same setup as you basically (win7 64 bit, avast) and I am also having issues but if I continue to try, I eventually get passed the "abnormal connection". Sometimes I don't get it, sometimes I do.