I just installed Mountain Lion, and now Drag and Drop doesn't work AT ALL. I have tried deleted the Cache files from HD Library as someone suggested. but still doesn't work, its not that it drag but doesn't drop, its doesn't even drag.. nothing moves. No its everywhere on the computer, sorry if I didn't say clearly it was generally not working I thought that was implied by the "AT ALL". Its a Macbook Pro 2009 2.4 Ghz Intel Core Duo 2GB 667 MHz DDR2 SDRAM. OS X 10.8 (previous OS was snow leopard).