In the cutscenes, the audio sometimes clip out. How do I solve this?

Try doing the following (if you're on Win7):

1. Start - All programs - GOG.com - Neverwinter Nights Diamond Edition - Settings.exe
When settings window opens, click on Change (lower right corner) - and choose Auto Detect option on Sound panel.

2. If it fails, Run the game as administrator, and when it starts from game menu, go to Options - Sound Options - Advanced Sound Options and try choosing one that works.

3. Also, there may be another really weird solution to the problem:
Start - All programs - GOG.com - Neverwinter Nights Diamond Edition\Tools and run NWN Toolset as administrator. When it open chose Start normally (bottom side of the Welcome window).