Sorry, this one might be a little tricky to reproduce. I can't always get it to happen, and I have not observed the behavior in IWD:EE on Linux. It didn't seem to take too long before it starts happening. It doesn't seem to happen immediately after just starting or loading a game. It seems to start happening after a few minutes, though.
This is under the Gnome remix of Ubuntu 14.04, nvidia drivers 343.22, GTX 980.
1. Scroll to left hand side of screen, very fast. ie rapidly move the mouse all the way from the right hand side of the screen to the left.
*Observed* Screen does not scroll to the left.
*Expected* Screen scrolls to the left.
When this starts happening, I can still scroll to the left, if I move the mouse to the left side more slowly. Scrolling Up and Left, as well as Down and Left can cause the problem to occur. All the other directions seem unaffected.