Well unless you have enabled the outbound protection in the win7 firewall (it is disabled by default), that shouldn't be getting in the way.
I don't use win7 so I can't be a great deal of practical help, so I can't say were the firewall settings are if you have enabled outbound protection. But you say you haven't changed them before, then outbound protection should still be disabled.
Have you installed any other software or made any other changes around the time that this started to happen ?
Unfortunately that's me for the night, almost 4am here, hopefully someone in your time zone with win7 can pick this up.