Time Server configuration - workstations not syncing with server

Hi,

I currently have a server setup as the time server (Windows 2008). If I go onto any of the workstations and enter "net time" it shows the correct time of the server as if it is linking correctly e.g.: 

Current time at \\TimeServer is 15/11/2013 09:24:55
The command completed successfully.

However the workstations themselves are always several minutes or more out of time (Although the Net time command seems to make out it is linking to this server). So it seems that it's not syncing correctly but pointing to the correct location

I do know that you can resync the workstations using a command per workstation but this will eventually go out of time again.  I need a more permanent fix.

Can anyone help?

Thanks