Option and shift keys down undetected

[David Epstein]

Using MC 2.5 on Mac OS 10.2, I have more than a few times had this
problem:  scripts that check the optionKey or the shiftKey detect them
as "up" even if they are in fact "down."  Restarting the computer--not
just quitting and relaunching Metacard--seems to cure the problem, but
then it returns.  And just now it returned very promptly.

The option key is not completely disabled even when this condition
strikes; for example, with the pointer tool selected, option-dragging
will successfully duplicate a button.

Is there a recognized cause or cure for this problem?

Many thanks.

David Epstein