Mouse is lagging on Mac Pro with 30" display

[Dae]

I've a Mac Pro 2009 with a Dell 30" (3008wfp) display. Runs on Snow Leopard 10.6.4.

I noticed that the cursor is retarded, it's lagging behind the mouse. It's clearly not an acceleration issue and I don't think I've ever since it before on other Macs — even though they all were with smaller displays.

USB Overdrive didn't help, but as I said it's not an acceleration issue.

Tried several mouses (Razer, Microsoft and Logitech ones), still the same.

Any ideas how to fix are appreciated!

 

[mrchinchilla]

Quote from Apple Support discussions: "It appears that if you have a second monitor connected that is not a high end computer monitor, the video card is not able to support the load and you will get lag on the mouse."

Have you tried using another monitor? What graphics card do you have? Suffice it to say it's definitely something to do with your graphics card or monitor.

Edit: Is it, by chance, a ATI 4870? Have a look at this thread: http://discussions.apple.com/message.jspa?messageID=11198058#11198058; they seem to have the same trouble as you.