This is clearly a mystery. I do sometimes receive the odd erratic behavior on my mouse and I'm running under Vista.
I haven't figured out as to what the problem is however I do know that it has relevance to irq's.
Delete the current software, keys in safe mode and connect the mouse to a different usb port other then the one that is designated for mouse use. Re-install the software.
Much of the interference should dissappear however I've installed Vista on numerous systems and the behaviour continued with the simplest mouse design's. It must be a compatibility/irq/driver issue within the operating system.
Still waiting for a solution.