is this on all folders? The only place where this TYPE OF (never heard of that one before though)behaviour is configured is
Folder > Tools > Folder Options > General, at the bottom, there is two options for opening (nothing like your problem), but hit Restore Default, or however you word it.
The other is Control Panel > Mouse.
The only thing that I think could cause that problem (if not in the mouse settings is)
a) You have a IntelliMouse, or equivilent, meaning one with its own control software, if so, have a look at the Mouse software, see if there is anything in there,
b) A virus...a pretty impractical one...but hey. Never know..do a virus scan.
Thats all i can think of. Never heard of that before.
Neil J Cotton
njc Information Systems
Systems Consultant
HND, BSc HONS, CCNA, BCS, IETF, DMTF