This is one of those setups that don't always work. Again from memory the video drivers (all drivers actually) must be compatible with said system.

There is no do-this cure here. Get a guru to update all the drivers proper (Microsoft update buttons or any "automatic" update is not to be used.)

Then when there are no PESTS (scan with EWIDO and HOUSECALL) and the VPN and PC ANYWHERE are the latest patched versions, make the call to Symantec about what they think the problem is.

In closing, other issues such as a too hot CPU was not mentioned by me...