Runtime error 9 - Subscript out of range

[RockstarRaccoon]

Ok, I thought there was a thread for this already, but I can't find it... I have had this problem before, but I don't remember anything about it.

I just installed DoomBuilder on a pc running Windows XP (I think MediaCenter), and there are three points when I get this error:
-Runtime Error 9-
Subscript out of range.

The times I get it are when:
1. I try to set the Boom IWAD to FreeDoom, which is on the desktop.
2. I don't remember the second one... I don't have access to that comp at the moment... I think it was something to do with loading a new map...
3. when I accidentally click for adding a texture in 3D mode. (because there is no IWAD of course, because I can't set it.

Now, I suspect that this is a file problem, or maybe there is a security thing here. Thanks