I have two monitors each with 2 desktops. In Lion, I was able to take, for example, an item from Desktop 2 of Monitor 2 and put it in Desktop 1 of Monitor 1. In ML, it's not possible to move from the desktop of one monitor to the other monitor. I tested this on a bootable Lion and it worked. I also tried with my MBA connecting it to my monitor and in that instance, it wouldn't work either. Lastly, I also did test with a new user. Anyone else notice this issue?