CDR Error used by “null”

I just started having problems with my CDRW and DVD-RW drive. Roxio Easy CD Creator 5.0 started giving me the error “No supported drives”. The drives are there but the show up as being in use by “null”. I have unistalled and reinstalled software;I have rolled back drive installations; I have run Norton System Works, and Virus Scan. I can’t seem to get “null” to let go of the drive. Are there any suggestions?