What is K3b? It is a free CD/DVD/Bluray burning program for Linux (it can be compiled for the Mac as well).
For the last little while, even before the last upgrade to the current version of Mint, I was having some trouble with the program. At first it no longer wanted to verify data disks. Just recently it wouldn’t even read the hard drive to pick up files to burn. It turned out the problem was a permissions thing. Unfortunately this was not something which could be easily changed from a user account. In the end running the program from the command line with “sudo k3b” fixed the problem. It presented a window which explained the permissions problem and offered to fix it. Now everything works again.