Delegates issues after installing update KB913807

I have been having issues with users adding delegates to their Outlook
2003 calendars after installing Update KB913807. They all get the
following error: "The delegate settings were not saved correctly.
Unable to activate send-on-behalf-of list. You do not have sufficient
permission to perform this operation on this object."

I have read on various posts that this can be resolved by removing the
update. Is this the best/only way to resolve this issue? However we
have been unable to remove it. It neither appears in Add/Remove
programs and removing it from the registry has no effect eother as it
just re-appears again after a reboot.

Any help would be appreciated.

Thanks

Joe