mouse cursor moves randomly and freezes machine

[Scanups]

I have built over 10 machines and this is the first one I have had a problem with. It has an Intel Pentium Q9650 3.0 Quad Core 775 chip on a GIGABYTE GA-X48 motherboard. I am running an EVGA 896-P3-1257-AR GeForce GTX 260 Core 216 Superclocked Edition 896MB 448-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card. It runs Vista 32 with service pack 2 and four gig of RAM and a Corsair 1000W PS.

No matter what I am doing, at some point, I lose control of the cursor - it just starts jumping around the screen in small increments. I have limited control of the keyboard - I have tried replacing the mouse on three occasions - both direct wired, usb and wireless - it is not the mouse.

Sometimes when I plug in a device, like a USB hard drive, the cursor will freeze until the device is recognized and then it's all right - but most of the time it just happens, and when it does, that's it - you can do nothing. On one occasion I had a window pop up telling me that my computer is slow.

Can anyone please help me - I appreciate it.