Outlook 2007: cannot expand folder ...pst is in use

[Grumpy Granny]

Error message when Outlook starts and when I try to access my pst from nav
panel or from toolbar:
"Cannot expand the folder. The file c:\Users . . .pst is in use and cannot
be accessed. Close any application that is using this file, and then try
again. You might need to restart your computer."

This is first time in 2 years of use that I have any error from Outlook.
Error continues after restart or full reboot. Open outlook, left nav panel
shows name of my pst file but will not expand the tree. Inbox and inbox
messages display in center panels, to do bar and task list display at right.

Local machine, Vista Ultimate 32bit, Outlook 2007, single user, single pst
file, business contact manager is installed but I do not use this at all,
Palm PDA with Chapurra Key Suite interface, no new files or changes in 2
years except MS updates.

 

[Gordon]

Palm PDA

Connected? That's what is using the pst file. Disconnect and see if that
changes the behaviour.

 

[Grumpy Granny]

No, the PDA was not connected, and had not been prior to problem starting. I
will note that possibility if same problem happens again.
Have restored pst file from shadow copy done 24 hours prior to problem.
(Most recent shadow copy produced the error also)

I am making the assumption that the pst file was corrupted, reason unknown.

Thanks for your response
Granny