Well, this wasn't the longest test but I played through one game of Dampiry after arriving at the castle and talking to Rhiannon.
Did the problem show up by then?
What is your mouse doing, just wandering all over the place?
One thing: I did not play with the patch.
I just clicked on the game icon and started it.
It played fine as far as I went.
What if you try it without the patch?
If it doesn't play without it, maybe you have a bad download.
Anyway, if nothing else, you might try downloading it again while you wait for a pro to help you.