Problem with 14MHz 65816 chip in ZipGS

["Rodney Hester" <rod3@mindspring.com>]

I currently have a version 1.02 ZipGS unit with a soldered 9MHz oscillator.
It came with the standard 10MHz 65c816 chip on-board.  I tried to replace it
with a 14MHz part from WDC (with the understanding it would still only run
at 9MHz - it was just the first step of an upgrade procedure), and with the
14MHz chip installed, the board repeatedly crashes into the monitor within a
few minutes.  The 10MHz chip performs flawlessly, even after 4 hours of
stress-testing followed by 12 hours of burn-in testing.

Am I looking at a static-damaged chip or the like here?  The chip has some
age on it, and to the best of my knowledge was never previously tested or
used - just kept in storage.  If it really is defunct, who still sells these
things?

Rodney