Can anyone tell me what I am doing/not doing that can cause this nagging problem. Each time I render (I'm rendering chapters one at a time) its a carpshoot as to whether or not each element will render or if I just get black with audio. Sometimes its the stills or b-roll that won't render, sometimes its the a-roll. Its different parts even when I'm rendering the same chapter!
All elements present/preview perfectly.
If I do a complete "clean disk" and a total reboot (not a restart) then more of the missing parts will render.
I have switched off the "Enable no recompress long-GOP rendering.
Computer is a: Dell Studio 540 Quad Core with 6GB Ram, OS= Vista Home Premium 64, Video card is an ATI Raedon HD 3450 (not the best in the world).

Is there a "clear cache after render completes" option somewhere in Vegas?