Problems burning bluray disks
Solution 1:
The answer to your problem is that the burning tool that is installed by default with k3b cannot write blu-ray disks. You get a whole variety of errors, like the ones that you described. To fix this you will need to install a different version of cdrecord. Instructions for this can be found here: https://help.ubuntu.com/community/CdDvd/Burning
Edit: Shorter version - add the following ppa and programs to replace the defaults using:
sudo add-apt-repository ppa:brandonsnider/cdrtools
sudo apt-get install cdrecord mkisofs