If you have a HyperCard stack that is over 700K, you may have experienced this
problem: when the stack is opened, it creates 100K or more of free space, thus
exceeding the disk memory capacity.
Normally, a HyperCard stack does not take additional disk space on opening. You
may find, however, that there is an "on openXXXXX" (XXXXX = Card, Field, etc.)
script in the stack that causes additional disk space to be used when the stack
is opened. Also, any change to the stack causes it to take up more room unless
it is locked via the Finder.