but each time I start K3b, some time after the splash shows up, the system freezes
There is a problem with splash screen. Try going to Settings/Configure K3b/Misc/Untick "show splash screen"
That might? help
It would be a good idea to delete the .K3b file if you re-install, not sure where/if it is in Gnome as I run KDE
https://bugs.launchpad.net/ubuntu/+sour ... bug/110484
""I installed AcetoneISO, after reading a review in Linux Format 92. One of AcetoneISO's options is "Burn CD/DVD", clicking on this launched k3b, but without displaying the splash screen and straight into the regular k3b window.""....