Time Sync issue on RHEL 5.3

Hi,

My Linux VMs are running on citrix XEN.Somehow the time drift is too high (going very fast). Even if the correct time configured using date -s command, for every 1 hr it is differing almost 5 - 10 mins.
Tried configuring ntpd (local NTP server) and still it is not synchronized.

Machine configuration:
OS: RHEL 5.3
Kernal: 2.6.18-128.el5
VM Product: XEN (Citrix)

someone please help me to fix this issue.
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Thanks and regards,
Uday

I am familar with VMware and the same problem sometimes occur in VMware. Here is a document which talks about the problem. It may point your in the correct direction.

Thanks fpmurphy.