I must be jinxed:( My new MacPro is having the same problems that I had with my G5 plus more…

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That's a good point too.

FWIW, I dropped the Logitech driver years ago. Not sure if it has become better. I use USB Overdrive and it's a very feature-filled and stable option. At least the last time I looked, it offered more features than Logitech's drivers... of course, it's not free. Just nagware.

Edit: Actually, another good step would be to create a new user and see if that user has the same issues.