Cannot Open Clipboard???

Sometimes I get a message saying "Cannot Open Clipboard".
Its completely random, it seems and doesn't happen enough
to get a complete handle on the situation at the time.

I just know that it has occurred both in CTRL-C type situations
and CTRL-V. The latter being an extremely small percentage of
the time.

I think its system related and would like to CLEAR the contents
of the clipboard prior to any CTRL-C operation. Is there a reliable
way to do this through code - an API call perhaps? I don't know
that this will stop the problem - I'm just shooting in the dark here.