Had a similar problem on kotor1 with dantooine beeing 'laggy'. Found some help on another forum. Surpridingly had the same problem on kotor2 and the same fix works. Involves changing items in the configuatation file 'kotor2' in the kotor file on your comp (normally lucasarts/kotor2)
-Make a copy for backup. Rename it and keep it someplace safe
-Open the original (should open in notpad)
-Go to the [Graphics Options] section, press enter at the end of this line to make a new line below.
-Add this line 'Disable Vertex Buffer Objects=1'
-Close and play!
Works like a charm on my comp.

Any problems let me know. I hope maybe it fixes your other problem too, I've only just started playing myself after playing kotor1 to death! Good luck!