Newbie Puzzled by Deleting Card

[dave.mckee at shaw.ca]

I have OS 10.2.1 running and am trying out revolution 1.1.1 and have run into something strange;

If I have 2 cards and each card has one button with the following script;

on mouseup
  delete this card
end mouseup

and then if I click on the button on either card, I get the following error;

 • There was an Execution Error at 9:45:15 AM
Error description:  Chunk: can't delete object
Object: button id 1005 of card id 1004 of stack "Untitled 1"
--------------------
delete this card
--------------------
Value: mouseup



What am I doing wrong ?  There must be something so painfully obvious about this that I just can not see why the script produces an error.