Dual Monitor Bug

Hey - I love this program and have been using it for a while. When I first started using this program it worked great without any problem. However, when I added a second monitor to my computer, it started to act strange. I can draw just fine over any program window open, however, if I go off the window and onto the desktop, or try to draw on the desktop, a very long horizontal line instantly shoots out to the right from where I first start to draw (or from every spot where I go off the window and onto the desktop). I was woundering if anyone else has this same problem when using dual monitors, or if this is something unique to my configuration/system.

Works just fine for me... (primary monitor on left side, nVidia 56.something driver)