Cubase 6.5 wont scroll in key editor

Hey Guys,
I’ve been an avid Cubase user for years, no pun intended. I’ve been using Cubase 6.5 for four years or so, never experiencing an issue like this.
When I’m editing midi in the key editor window, I will select a group of notes and move them up or down an octave by holding shift + up arrow. After I do this, the mouse wheel doesn’t work. Then if I grab the vertical scroll bar and attempt to move it, or use the hand, it shakes, like it doesn’t want to allow me to move for some reason. I will move it, but as soon as I let go of the button it jumps back. This problem only occurred in the last week or so and I cant figure out what I did.

I had messed around in the preferences menu but I cant seem to find anything relating to this problem.
Help would be greatly appreciated!

Joe