Why are my servers clock out of sync?

The domain time is now out of sync by 4 mins and its getting on my nerves, I ran a quick check to see if I could determine how much it was out by exactly and got this back:

H:\>w32tm /stripchart /computer:time.windows.com /samples:5 /dataonly
Tracking time.windows.com [65.55.56.112:123].
Collecting 5 samples.
The current time is 31/08/2011 09:46:29.
09:46:29, error: 0x800705B4
09:46:32, error: 0x800705B4
09:46:35, error: 0x800705B4
09:46:38, -241.8117870s
09:46:40, error: 0x800705B4

I get the impression that packets are being dropped, but have no idea how to determine where the packets are getting dropped. Our internet connection is a good high speed network where we don't notice any issues. Could this be an IPv6 thing where its trying that first?

The errors are because the query is timing out. Try querying time.nist.gov, or pool.ntp.org instead of time.windows.com. Or look on http://www.pool.ntp.org/en/ to select a time server near your location