(The following is a direct quote from a reply to an email on the MailingList)
Writing optical media in 2.6.8 and 18.104.22.168 are indeed somewhat broken. 2.6.9 is broken for a few drives. 2.6.10 should fix most of the rest. However, the nature of the [known] breakage is that it won't write at all.
I'm sure I've posted this before, but what happened was:
Someone noticed in 2.6.7 that due to CD-writing requirements, you could send (e.g.) FORMAT-MEDIA commands to arbitrary devices. Now, this is fine for CD-RW media, but tends to damage hard disks quite badly. Other SCSI commands, equally destructive in the wrong circumstances, were also permitted. This is obviously a *major* security hole.
In 2.6.8, the hole was closed by preventing non-root users from writing these commands to any device. This, naturally, closes the security hole, but prevents ordinary users from writing CDs. Two fixes are to run cdrecord as root, or to set it as setuid root. Neither of these is recommended, as there is at least one known security hole in cdrecord that allows privilege escalation.
In 2.6.9, most of the commands used by cdrecord were again permitted for ordinary users when they are applied to optical-media recording devices. However, since different drives use different sets of commands, some of the more obscure devices still don't work. 2.6.10 should get most of the remaining commands needed for remaining drives.
If you're seeing failures to write DVDs that start working but produce a coaster, that's not the 2.6.8 CD-writing problem – that's something else. If it fails when trying to read the media size, or when formatting an -RW medium, then that _is_ the 2.6.8 problem biting you.