Vista - pc freezes with vnc or any network or media sharing

I have a new pc x64 running vista home premium. I am new to vista with this pc.
My problem exists in several situations. The problem is the pc freezes or locks: screen, mouse, cannot ctl-alt-del, but I can still hear the fan and drive running. The pc can sit like this for several minutes: 10 to 30 minutes or longer. Then it reboots with the message: windows has recovered..... the error given is blue screen.
I looked at the administrative error logs and nothing jumps out at the time it does this.

The situations in which it does this is when network sharing files: from laptop on same network.

When using a vnc on the same network and another network. I have tried tightvnc and ultravnc.

It also does this when using orb to stream media such as music and video to my iphone via winamp remote and orb.

I get a good connection with all these for 2 or 5 minutes before the pc locks. I have even connected with vnc, manually disconnected, then reconnected then disconnected..... But if I let it stay connected for several minutes it locks.

I have run malware/spyware/antivirus: malwarebytes, spybot, spyware blaster and my antivirus/firewall is Bitdefender. Bitdefender is the online one with realtime protection. I have used all these for years with xp.

I have updated my ethernet adapter driver.

Any ideas? I am at a loss.

Thanks in advance.

jt