I keep getting a weird error in XWE

Whenever I open XWE, it shows an error message that says "Failed to create key .WAD". When I hit OK on that box, it'll pop up with another error saying "List index out of bound (0)". Whenever I try to open any other wads, it'll pop up with "List index out of bound (3)" and it'll freeze afterwards. What's going on and how can I fix this?

I'm using Windows Vista.

Try what is suggested here.

I got XWE working again.