As far as I remember this heappen when you extracted root BGSwitcher folders from archive directly to Scripts folder. It was my fault to call both root and inner folder with the same name "BGSwitcher":( By igor_grinchesku at 2011-05-19
I was copying the script into the startup folder, muscle memory. Fixed now, but damn that's a lot of color banding on this gradients if you have gamma correction on, so make sure you turn it off.