Deleting message in outlook 2002

Hi

I have a user who want to delete some of his messages uisng a right click on his mouse or just simply clicking on Delete button in the Toolbar. However the outlook gives an error message that says”The messaging interface has returned an unknown error.If the problem persists restart the outlook”. I used office repair tool to fix it but it did not help. I also tried to re-install the outlook. However the error did not dissapear. When using Shift+Delete message it deletes without any problem. Can anyone advise what it might be and how to fix it ?