Creating rules hangs notes

Notes is hanging whenever a few of the users try to create mail rules on the clients. Usually there’s no error message and we have to zap notes to get out.

However, I got the error:

Error in CompactMailRules function 91: object variable not set.

The user was creating a rule where similar to

sender was johndoe@abc.com then put in folder Personal\folderforjohndoe

Thanks for any help on this.