Thanks to the users who sent us their MediaLab+Inquisit folders to play with. We think it has something to do with Inquisit 3 and the way MediaLab calls Inquisit sessions. It used to be that MediaLab could automatically detect the location of Inquisit.exe, but now it can't--this results in the file not found error. I think it has something to do with registry entries that are made during the Inquisit 3 installation. Consequently, the version of MediaLab you have probably won’t make any difference. I just emailed Sean Draine and he said he would look into it and see if he can find a fix. As I mentioned above, he's usually pretty quick to take care of stuff like this once we figure out what's going on.