RDC stops working after Win7 migration from WinXP

I'm getting the following error after upgrading my machine to Win7x64 Ent. "Your system administrator does not allow you to connect to this remote computer. For assistance, contact your system administrator or technical support."

If I modify the .rdp file to include EnableCredSSPSupport:i:0 I am able to remote to the target machine.

Any ideas on how to troubleshoot this?

Thanks,

Brian