Cannot alter user email profiles

I'm having an odd problem with user profiles in outlook 2003 when connecting
to our exchange server. Some of the users just stop being able to connect to
the server and when you go into the control panel, mail, to alter/check the
email account the window crashes with a run32dll.exe error. The pc can ping
the mail server ok and the really weird thing is if another user signs on to
the pc they can access there email ok. If you delete all the workstation
profiles and recreate the outlook exchange server connection it sometimes
lets you access again - but usually does not. The passwords and user names
are ok - as users can access via Outlook web access. I have tried quite a few
things - like using the new profile switches when starting email, and also
registry scans but to no avail. Does anyone have any ideas?
Thanks