I assume you've read the VMware guide to time sync issues? I've found it helpful when I had similar issues, but not helpful enough. In one case, the clock was slipping enough that the recommended kernel timing parameters and ntpd was not able to correct it, and the user finally gave up and just ran 'ntpdate' via cron every 30 minutes to forcibly set the clock (with all the usual problems that jumping the clock can bring).