mx518 help wanted

A couple of days ago, I bought myself a nice mx518, i thought my old 510 was a bit out of date.

I quickly noticed that it wasn't what I've expected.
From time to time the mouse was just beeing fucked. I mean seriously. If I turned right, my mouse turned left.
And I can't reproduce this error. It only happens when I don't expect it to happen.

I installed the drivers who are located on my cd, I downloaded an update and installed it + reboot, hell, I even configurated it manually ffs.

Can someone help me?