I have the same issue. Autdodesk suggests turning off 'Press and Drag' but it didn't help for me.
I found that if I dock my QAT at the bottom, the problem stops.
Hope it helps
I had this same problem and at times I had to move the bar at the top of the screen to the bottom. that seem to fix it
I have encountered and resolved this on many machines and operating systems. If you go to the display Setting/Screen Resolution setting (right click on you desktop) Then change the alignment of screen 1 to screen 2 (you probably have them aligned on the bottom or the number 2 display below the diplay 1. Try aligning the TOP of diplay 2 with the Top of display 1
The frustrating part is this problem began with Revit 2010 and yes it still exists in 2012... But it must be Microsoft's fault <rant rant rant>
Good Luck killing the 'Jumping Beans'
I had the same problem when I attached my second monitor to my laptop. At home everything went fine, there I use a HDMI cable, at the office I had to use a DVI cable.
So using a DVI cable solved the problem for me. Hope this helps guys.....