With a Logitech cordless mouse, sometimes the pointer freezes on the screen until a mouse button is clicked.  The receiver is on the desk, 2 foot away, in a direct line of sight.  It can occur when the pc is being used - ie it's not after a period of inactivity where kit might have gone to sleep.

Stuff done so far:
new batteries (even though the cordless mouse is rechargable, and there is no battery light on it)
replaced entire mouse, kbd, and receiver with a new Logitech version (similar but updated model).
checked Task Manager - no high utilisation of other apps.  
Event Log is tidy enough - no related faults.
checked mouse mat is not affecting it - it is a leather style one, on a leather executive desk, but both were in use for many years till this started a week or so ago.  
Setpoint software is recent - 2.11 - but I'll be updating this to 2.20 just for fun later, but I don't think this will fix it so I'd like some new ideas...

System - HP DC 7600 small form factor, running Win XP Pro SP2, patched up to date.  No other recent changes to environment - ie no new software, kit moved, etc.