Active Directory

I am having difficulties trying to join a Mac Pro desktop back to the domain. I've gone thru both system preferences and Users & Group and used Directory Utility to join it back to the domain but it still continues to give me "unable to connect to server". I can ping the server from terminal from the workstation so it can talk to it.

Is there a way to get rid of all previous active directory bindings and completely reset the computer name so I can rejoin it back.

Thanks in advance for any sights and help!

Did you delete the Mac computer object from AD?

Is the only DNS server on the Mac the domain controller?

Yes the Mac Computer has already been deleted from the AD as well as all DNS records.
And yes that is the only domain controller.

I remember there being a plist file related to directory binding.
Look in /Library/Preferences, I'm pretty sure it's in there. If you find it, back it up and then delete it.
Reboot and try again.