I'd post this on the Nexus thread, but I think I'll get more help here.

I broke down and decided to try MTES4 to keep a separate install for testing and editing, so I don't screw up my game. Unfortunately, I didn't get any further than creating a dummy folder and trying to switch to it when I got this error message: http://imageshack.com/a/img600/4458/t6f5.jpg I have no idea what's causing it; I tried it without any other windows open and nothing running, but it still refuses to switch. What am I doing wrong?