Firewall mimics driver problem and ctd

I just upgraded to a whole new system, Intel E6600 / 4GB Ram / Nvidia 8800 GTX / Vista 64. When I loaded up FSX I was getting flickering and an occassional ctd. I thought it was a driver problem. Then I discovered that I had both the windows Vista and Norton firewalls enabled. I turned off the windows firewall to avoid conflicts but I didn't realize I had one with FSX. Disabling one of the firewalls fixed the video problems and ctd in FSX I was having. Who Knew? FSX runs like a dream, smooth as a babies butt and dazzling to the eye. I was wondering if someone else out there was having a similar conflict and didn't know it? Hence this posting.Al