Throwing exception

Everytime I try to close a table with nothing on it, the systems throws exception and forces close closedown. the close button works fine when there is something on the ticket but when iit is empty it doesnt

Is it possible to show us the exception report?

Thanks Emre, I have sorted it now, I forgot I tried to set it up so that another user can log in and do something then the original user could log back in to what they where doing. But I couldn’t get it to work. I have removed the rule I set up and it has gone back to normal.