Running Outlook 2003 SP2 on Windows XP - all patches -, Exchange 2003 SP1
(Enterprise) on Windows 2003 SP1 - all patches except SP2 for Exchange.

I have a number of users that are unable to change their delegates, edit the
Out of Office rules, etc. When they try, they get the following error
"Unable to activate send-on-behalf-of list. You do not have sufficient
permission to perform this action on this object"

There are no errors at all in the Exchange server logs.

This has only just started happening - but does not affect all users.

Can anyone shed any light on what causes this and how to fix it?

Any help appreciated.

Mike