I've been suffering from this bug for a while on specifically World of Warcraft. Basically what happens is, the cursor will every once in a while reset to the center of the screen. This is became (still is) very annoying.
I went to the Warcraft tech forums and asked about this problem, and as I was firstly suspecting that it could be Logitechs driver for the MX518. So I reinstalled it, still getting the reset.
So, I googled this problem, and in the first few topics that show up on the list, it was a you tube video posted on March 22, 2012, that sure enough described the exact same problem I'm currently having, along with a fix.
The link to it is: http://www.youtube.com/watch?v=qKmXs7Bt4L8
Titled: (Fixed) Mouse cursor reset bug with mumble(overlay)
Here's the description by the author:
Published on Mar 22, 2012 by fastjan
Whenever cursor goes hidden, it randomly resets to center of the screen. I found that mumble's overlay seems to interfere way more than others, even though it is disabled in the options. Shutting down mumble all together makes the issue extremely rare.
As you can see it's pretty annoying specially when it tilts the screen to random position.
Games that always hide or show the cursor are not effected by this.
Fix for Mumble: Download the latest beta version for 1.2.4(it might be named as 1.2.3etc, but installer will say it's 1.2.4), regedit to HKEY_CURRENT_USER\Software\Mumble\Mumble add string value "winhooks" and value it as "false".
I'm personally weary about messing with registry, instead I called someone from typefrag, and he pretty much lead me here, that is after helping me with what he could of coarse.
Other notes: I too like in the description, have noticed that this does not happen at all at least for me when I have Mumble closed / turned off.
As for the beta, I can't seem to find one, if there's a link available to the public I would love to try it out.
Thank you in advance.