I had been on line for several hours and all of a sudden the mouse would only move up and down in the exact middle of my screen. I have unplugged, replugged, uninstalled, reinstalled, etc. I didn't have another computer or another mouse to try but will borrow a mouse this afternoon to see if that is the issue. In the back of my mind - I may have held down keys and mouse buttons at the same time...could a multiple key stroke have caused this? It isn't erratic movement - just vertical.Last time I SAW this it was a ball mouse that has hair wrapped AROUND the 1 of the encoder wheels inside allowing only for left to right motion with no up and down. I had X but no Y axis control and you NEED both to move to position instead of linear verticle or horizontal only.

Swapping mouse should fix.

This is likely not malware etc like the DRUNKEN mouse etc and just a bad mouse. Only if you see a cropping box display with mouse have I ever seen a keyboard mouse combination error.

Or you could just clean it out if its a ball mouse. If its not try a new oneI took a closer look at the mouse ball - and sure enough found a hair wrapped around the wheel inside - it works perfect now! THANK YOU!
Nice to know it wasn't the metal plate in my HEAD...lol....