Office XP sp3 (Outlook 2002) non Exchange

I have a network user who cannot create an appointment in his Outlook
Calendar.
In Day/Week/Month view, you can type in an appointment, but within a few
seconds of hitting Enter, the label disappears and nothing more appears to
happen. The monthly calendar shows bold, indicating an appointment for the
date, and trying to enter another appointment on the same time on the same
day generates a warning that there is an existing appointment. However there
is no visible sign of the appointment.

Now this is not an exchange setup, but the user has a roaming profile and
can access his outlook .pst file from any workstation. This happens on all
workstations he logs into.

Other users on the same workstations do not exhibit the problem so I don't
suspect the Outlook installation.

It seemed apparent that the user's .pst file was implicated so I have tried
the following...

1
Ran scanpst.exe on his .pst file. I corrected a few minior errors but did
nothing to solve the problem
2
Re-named his .pst file and substituted a template .pst file that we use on
new accounts.
This did not solve the problem.

I'm stumped - any suggestions?

--
Geoff Taylor BSc Dip Ed