Following the advised tweaks for cfs.config, I set composite terrain texture pool, Composite aircraft texture pool, Vertex Buffer pool and Index Buffer pool from default to SYSTEMMEM. Now I get buildings and trees flashing on and off. If I set them back to default, then everything is fine. Anyone else getting this?

The unticked Dual Pass Render and ticked High resolution Z-buffer tweak works perfectly.

My motherboard is a 1 Gig Epox NForce 4, with AMD64 3400 and a 256 mb GeForce 6800 GT Graphics card. I'm running Direct X 9.0c.

That particular tweak guide was published in PC Pilot Jan/Feb issue 2003 - the same issue that carried the review of the CFS3 Sim. I sort of figured that this made the tweak guide fairly official. I shoulda known better 8)

Absolutely right - The Geforce 6800 GT is awesome. But when I first loaded up CFS3, it would freeze or crash, or send out flashing black lines at me,  until I set it up with an unticked dual pass render and a ticked high res z buffer. I also had to set up  the 6800 with High Quality as opposed to Quality.

Since you're using the same graphics card, perhaps you could advise me as to what settings you have selected for both the 6800 GT and the Sim itself? Did you not have problems at first?