I have one user running Windows 7/64 who can operate normally in the Notes client for about a minute before the mouse stops working.  I should clarify, he can still move the cursor, he can actually select a document, but when he double-clicks, we just hear the warning ding, and nothing opens.  Furthermore, pressing Enter does not open the selected document; it just generates a ding.  He can't open a Notes application from a bookmark. Clicking on something in the dropdown menus (File, Edit, etc.) makes them appear selected, but no menu drops down.  Right clicking does nothing.  In short, he can't do anything, and has to close Notes and reopen for another minute of use.

I upgraded him from 8.5 to 9.0.1 and the issue persisted.  I wiped out desktop.ndk and bookmark.nsf, and most of notes.ini and went through setup and it didn't help.

Switched from a Logitech mouse to a Dell mouse with new driver.  Same thing.

Everything in the OS and other applications still work normally.

Any suggestions?