Do you get prompted with "Do you want to start Outlook in safe mode?" If so,
what happens if you click "No".? Do you get a different error message?
If using 2003 with Exchange, is Cached Exchange Mode turned on? If so, try
running scanpst.exe on the pst file.
Could try some switches like "outlook /resetfolders" or "outlook
/cleanprofile".
More on switches:
http://office.microsoft.com/en-us/assistance/HP010031101033.aspx?mode=print
Could try deleting the outcmd.dat file (C:\Documents and Settings\<User
Name>\Application Data\Microsoft\Outlook).
Could try creating a new profile in Control Panel->Mail.
Let us know if you have any questions on any of these.
