Even though the mouse jumps are not that ocassional, they can get annoying at times so a fix would be nice. So if I delete the AppleUpstreamUserClient.kext kext, will the mouse stop jumping around? If so, what does this kext do? Is it safe to remove? I want to make sure before I delete or rename it.

The kext suposedly handles hdcp checking and enforcing when playing hd video to a external monitor over a digital connection.
It causes lag only with certain nvidia gpus and while quicktime/itunes is running.
Better to use a disabler than deleting it, so you are protected for future system updates.

What disabler you mean? BTW, I am running fully vanilla, 64bit.

Edit: The problem occurs only when iTunes or Quicktime is open. It is minimum, but noticeable at times. Either way I found the fix.

What was the fix you used?

You found the "fix" and did not bother to share it ???

Here is the one I use.

I'm using the same one that Chico posted below.

http://osx86.sojugarden.com/downloads/

Here is the link to the fix I found:

http://osx86.sojugarden.com/files/Ex...abler.kext.zip

Hello Guys,

I had exactly the same problem, noticeable lag all i did was remove the appleupstreamuserclient.kext, and that fixed the problem, but just rename yours and fix permissions on the drive to test..

Worked for me so everyone else should be good to go with that fix!!,

Cheers,
Rich.