Vista Machine freezes with mouse activity

My environment is Vista Ultimate running on an Intel D975XBX2 motherboard

with an E6600 Core 2 Duo processor and 2GB of DDR2-PC6400 [800] memory the

graphics card is an ATI Radeon X1950 Pro-512MB. The situation is that the

machine will freeze at different times [requiring a hard shutdown] most

noticeably when I have double clicked on something. At first I suspected my

Microsoft Desktop Elite mouse/keyboard for Bluetooth because the mouse would

move erratically at times. I eliminated the Bluetooth devices [and dongle]

and switched to a PS/2 keyboard and a USB wheel mouse.

At first the problem seemed to go away, but that was misleading it has

returned with a vengeance. Just opening Outlook 2003 and clicking to open an

email can often trigger the freeze. I have now eliminated all USB devices by

installing a reliable PS/2 mouse. It has now been several hours without a

lock-up.

Yes, I have already installed the most current Intel BIOS and my Vista

installation is current with updates, including the reliability / performance

fixes released two weeks ago. Yes, I run an up-to-date CA A/V application as

well as CounterSpy, and have run several different online scans without any

malware being discovered.

I certainly suspect driver involvement, especially the USB drivers, but I am

uncertain how to proceed, or how to diagnose this problem any further. Any

help from the driver and/or Intel experts out there will be most greatly

appreciated.

Thanks in advance.