There's a workaround explained here:
https://help.ubuntu.com/community/CdDvd/Burning#Blu-Ray_Burning
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https://bugs.launchpad.net/bugs/484479
Title:
K3B does NOT deal with Blu-Ray blank
Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: k3b (Ubuntu)
Status: New = Confirmed
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https://bugs.launchpad.net/bugs/484479
Title:
K3B
** Attachment added: Dependencies.txt
http://launchpadlibrarian.net/35802052/Dependencies.txt
** Attachment added: ProcMaps.txt
http://launchpadlibrarian.net/35802053/ProcMaps.txt
** Attachment added: ProcStatus.txt
http://launchpadlibrarian.net/35802054/ProcStatus.txt
** Attachment