Might help to know the operating system you are imaging and also the operating system and environment that your servers run. Are you running AD or a regular domain architecture. Are you using an account that has the necessary privileges to join a machine to the domain.
Is the old instance of that machine name being deleted from the domain or AD prior to re-imaging (very much a necessary step IME).
If the machine does not auto-join the domain during sysprep, are you able to do it manually using the same account as you defined for auto-joining, once the machine has rebooted?  Is the machine able to get an IP address - which presumes that the NIC driver loads OK using PNP.  Try checking the event logs to see if there are any error messages in the System, Security or Application event logs, which might shed some light on the problem.

Sorry for not being more specific... machines are XP they are part of a 2008 Windows AD network. The account is a domain admin account and yes I can add the machine to the domain manually once the process has completed. I have not deleted the old instance from the domain so I will try that now thanks for that! Have not checked the logs but should I create a custom template with the proper machine/domain settings and attach to the instance? I have read where you should only refresh the configuration and not keep the domain settings in the clients config?

Thanks for your time!

I take the adding to the domain part out of sysprep and use a configuration task in ghost. If you make a new taks and uncheck all the boxes except for Workgroup/Domain membership (just put the right information in that box), then when you image just add configuration to the imaging task, use a template and select the right configuration, make sure to check the box at the bottom that says Use dfault settings. Its worked well for me in XP/Vista/7. The machines will reboot a few times after imaging but they should end up with the old name and on the domain.