Ati 4870 Monitor/Mouse problem

Hi!

I have one Mac Pro Quad Core Nehalem 2.66Ghz with one ATI 4870 connected to two Acer Al2423 (1920x1200 at 60 Hz). One is connected using DVI cable and the other with the adapter Mini display port/DVI.

The problem here is the mouse movement, if you try to follow a straight line with the mouse (mighty mouse) the pointer jumps forward some times more rapidly than your hand movement. Imagine you want to select one button in some software and when you stop the mouse to click that button the pointer stops some inches after or behind... i'm getting nut with this thing.

Apple on the phone can't fix this thing... tried lot's of thing's: change ports, connect/disconnect, new OSX install (10.5.6) the 10.5.8 don't change nothing at all... with one monitor connected on the the DVI port or using only the Mini Display Port...

I have BootCamp installed with Vista Ultimate 32 Bit. and the mouse works very nice there but in OSX just jumps and moves erratically.

I visited a technical Apple center this morning and they didn't find any problem, i tested the machine with them and the mouse was very fine, not a single jump, using my keyboard and mouse and others in the center... they have the monitor there connected with VGA adapter.

After this journey changed the cables from DVI to VGA, with the adapters from DVI to VGA and MinDisplay Porte to VGA (on the two monitors) and the problem goes away... bad drivers from Apple/ATI?????

What can i do to solve this thing?

Regards

p.s. - Snow Leopard didn't solve this thing either