While surfing around the web we found various different firmware versions (Click on the version numbers to download firmware):
Mitsumi CR-4809TE version 1.0E:
Upgrades media database to support new media.
Mitsumi CR-480ATE version 1.0E:
Disk repair functionality improved.
(Mt.Rainier)Disc Detect improved.
AOpen CRW2440 version 2.06:
No changelog yet.
Philips CDRW1610A/CDD4911 version P1.4:
No changelog, but we know that some of you have problem with this drive when it comes to media compatibility, so it may be a good idea to try this new version.
Source: The firmware page