Exchange 2010: BPA error: "Active Directory domain 'XXXX' has an unrecognized Exchange signature Current DomainPrep version: 12639."

Don't worry!

The Best Pratice Analyzer from toolbox, returns following error:
"Active Directory domain 'XXXX' has an unrecognized Exchange signature. Current DomainPrep version: 12639."

This a known issue now and will be fixed in SP1 for Exchange 2010.