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

[M]

> 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.
> [...]

I was having the same exact problem on Debian which was running on Xen. 
Removed ntp as the ISP:'s admin recommended, that did not help. Then 
they moved my virtual machine to another host and everything was fine 
for a while. As for now the problem is occuring about once a week, two 
or three error messages.

M