2011 Mini i7, 8 gB RAM, 750 HD, OS 10.8.1. At random, files moved from a folder on the desktop will be thrown to the upper left corner of the screen and barely visible. i moved a group of files the other day and not only did this happen but the files were all piled on top of each other and had to be sorted out after moving them back onto an open area of the screen. Has anyone else had this experience. I believe it actually started some time after installing Mountain Lion.