I use Ubuntu 12.04. Today I tried to burn an ISO file in a DVD-R disk using K3b. It used to work, but today, after one and a half minutes, it stopped saying that "cdrecord has no permission to open the device". I searched for a solution, and I found that I had to do something with k3bsetup. I tried to use it, but I had no idea what to do, and I couldn't find a guide, so I checked cdrecord and clicked apply. Now there is another error; it says "cdrecord returns an unknown error! (code 254)". What should I do?
I had similar problem and fixed it with the following steps:
Open k3b. Go to Settings -> Setup system Permissions. Select all options and apply.
It will ask for your password (you must be admin).
If it doesn't works, open k3b from terminal with sudo k3b, and try same steps as before.