To help you out, look at the scanner log (xxxx_RetinaScanner.log in the Logs directory) and search for CreateRegSession. Examine the error code (err=xxx) at the end of the line and post back to the forum what it is. There are several things that could cause remote registry access to fail.
Also look for an entry like "OSDETECT_PHASE ....... Target OS (????)" and post the entry.
Craig