Logitech MX620 mouse freezes my iMac

This is a problem that has been more or less constant for months. Our otherwise no-problem Intel iMac has had intermittent freezes requiring hard restarts without apparent provocation. These usually present as a blank blue, white or black screen and have seemed to be associated with use of our Logitech MX620 wireless mouse. I have run Disk Warrior, applejack and Cocktail numerous times and turned up nothing. We updated to Lion last week without problems but the freezes continued almost daily. I updated the Logitech Control Center software to the Lion-compatible version but that didn't help.

So I disconnected the Logitech and reconnected the wired Apple mouse that came with the iMac. No freezes since I made the change.

Any ideas?

Thanks.