Thanks for replies. Zyndstoff, you are correct. I had the same problem with Avast 5+ and FF 3+. This problem has been posted by others previously and I wonder if others also experience this.
I use nothing else but avast and win firewall, have cleared all dns caches, reset winsock, etc., and the problem continues.
It's a minor aggravation but possibly needs further developer attention, or I'm missing something.