I hit the same problem a few hours ago. I don't know if it is too later to be of use to you but hopefully it will help anyone else who hits this problem.

My guess is you also had a very sluggish keyboard when typing in your profile name at the start too.

Anyway the problem is caused by a mouse polling rate in excess of 500Hz. You need to use what ever utility your mouse came with to reduce the polling rate below 500Hz. For me the best option was 250Hz which fixed this problem.

You might also want to play around with the DPI settings of the mouse for this game I found a lower DPI helped.

This is the original post on the steam forum from the dev with a suggestion of a utility which might be handy if your mouse is a logitech.

http://steamcommunity.com/app/46260/discussions/0/666828127020442955/

Hello. Maybe I've found a solution for our problem.

Bought yesterday and got the same sluggish mouse and fps behavior.

So, since I installed this version of Wine for Windows the fps is now consistent and the mouse movement is soft:
http://adolfintel.com/index.php?p=wined3d/index.frag

Please see the readme to know what install. Fair easy!

I have the same problem and a very similar configuration of my PC.

There is no extra driver for my mouse that allows to change dpi or frequency, and changing the mouse settings ("“enhance pointer precision”) allowed by win7 doesn't help (but makes my mouse sluggish in other apps)!

Running the game as admin doesn't help.

It seems, that this problem was also present in Star Wolves 2.