"Your system clock just jumped" on Debian+VMware ESX

[Lucky Green]

I am seeing the following errors in the Tor log:

[...]
Feb 28 04:54:43.008 [notice] Your system clock just jumped 4398 seconds
backward; assuming established circuits no longer work.
Feb 28 04:54:46.020 [notice] Your system clock just jumped 4399 seconds
forward; assuming established circuits no longer work.
[...]

Tor version:
Tor v0.2.0.20-rc (r13715)
Standard Debian package

Guest OS:
Debian etch
Kernel 2.6.22-4-amd64

Host OS:
VMware ESX 3.5
VMware Tools installed

NTP:
ntp is installed on the guest. ntpq -p shows a solid lock.

Details:
I recognize that there have been long-standing issues with system time
on VMware Workstation. Though I don't believe this is the case on ESX,
certainly not with VMware Tools installed.

I ran another Tor test server on this very same ESX host (though
different VM) for a couple of weeks earlier this year without issues.

Does anybody here have a suggestion how to determine root cause?

Thanks,
--Lucky Green