That's a known Vista isssue. From the Bioware forums:
Find the NWN2ToolsetLauncher.exe file in your Program Files (x86)AtariNeverwinter Nights 2 directory. Right click on it and bring up your properties window. Under the compatability tab, tell it run in compatibility mode for XP (SP2) and to disable visual themes.
- Curmudgeon
HDM ALFA 03 - The Silver Marches
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ "Maxim #12: A soft answer turneth away wrath. Once wrath is looking the other way, shoot it in the head." - The Seventy Maxims of Maximally Effective Mercenaries
"This is not my circus. These are not my monkeys."