Are you running a 64bit system ? KB:TL was never good with those. I was lucky with mine. AP and Crossworlds are newer and specifically built to run mainly on such systems.
Otherwise try a partition with a 32-bit system. XP has by far the least sources of errors with KB:TL.
Try turning off antialiasing and V-Sync and check if the errors still appear.
Get the latest drivers for your hardware (not only video card but also sound chip).
Use Nvidia graphics cards
