clock drift at embedded XP

Hi 
I am using Windows XP Embedded on my machine which is installed from a backup image.
Recently, I have detected a system clock drift on my machine. this drift is very large ( one second at every 5 minutes ).
This drift is not permanent, it randomly happened at every bootup.
But if the unit bootup with drift it stay until the next bootup.
Another important thing is that at the bootup the unit starting with 0 delay every time, for example:
booting up the unit.
world time is 12:00:00.00, unit time is 12:00:00.00.
wait for 10 minutes.
world time is 12:10:00.00, unit time is 12:09:58.00.
turn off the unit 
booting up the unit.
world time is 12:15:00.00, unit time is 12:15:00.00.
I can't us clock synchronization.
I installed regular xp ( not embedded) and the drift did not appears.
Can someone give me any help on how to find the root cause of the problem and how to solve it at the Embadded XP?