Following was pulled from a post in the Google archives - Try these options, though I would personally try finding and renaming the outcmd.dat file first before running through this lot. If it doesn't work after that, then try these as listed:-
Close outlook, find and delete all these files in a single attempt:
outcmd.dat
extend.dat
frmcache.dat
Now try and launch Outlook normally, Do you still have the same problem?
If yes, then go to start > run > type "outlook /safe", hit ok, same problem?
if not then some add in may be the cause of this issue.
go to outlook > tools > options > other > instant message > uncheck the
related box to disable instant messaging, then click on advanced options >
add ins manager > enable/disable add ins here one by one, restart outlook,
try to find the faulty add in in this way.
Regards
Ken..................