time fluctuates

[Vin]

The time fluctuates, somtimes it's 5 minutes slow other
times it's 13 minutes slow then it's jumps back to 7
minutes slow.... it goes back and forth never fast
though... now this computer is on a company network and
the time sever is enabled and when i tell it to resync it
changes to the right time but later on the time still
fluctuates... it never the slow by the same amount...
and hints???

Thanks
Vin