Whenever a CD or DVD is inserted into the drive and mounted, wodim fails to recognise the device unless given root previledges. I have two optical drives (a master CD writer and a slave DVD writer) and I have just inserted, mounted and then ejected a CD into the CD writer. This is the result for the command wodim -scanbus as a normal user
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badshah@linux-vulp:~> wodim -scanbus
scsibus4:
        4,0,0   400) *
        4,1,0   401) 'HP      ' 'DVD Writer 1035r' 'NH21' Removable CD-ROM
        4,2,0   402) *
        4,3,0   403) *
        4,4,0   404) *
        4,5,0   405) *
        4,6,0   406) *
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Clearly the CD writer is not detected.
As a super user the following is the output of the same command
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linux-vulp:/home/badshah # wodim -scanbus
scsibus4:
        4,0,0   400) 'SONY    ' 'CD-RW  CRX320EE ' 'RYK4' Removable CD-ROM
        4,1,0   401) 'HP      ' 'DVD Writer 1035r' 'NH21' Removable CD-ROM
        4,2,0   402) *
        4,3,0   403) *
        4,4,0   404) *
        4,5,0   405) *
        4,6,0   406) *
        4,7,0   407) *
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Under such circumstances cd or dvd writing becomes impossible as a non-root user. It takes a restart for wodim to recognise all drives correctly again. If both devices are mounted and then ejected, subsequently wodim does not recognise a single device as normal user rendering cd/dvd writing impossible.