This one worked for me:
Close the Sonic RecordNow! error message so the application will shut down.
Open Device Manager
Disable your CD/DVD burner
Enable your CD/DVD burner again
Restart Sonic RecordNow!
And then it worked.
This was after a clean install on Windows XP SP3 with Sonic RecordNow! version 7.22 (Build 720B41P).
Hope it helps you out too, good luck everybody.