I just ran into the problem with MakeMKV hanging like has been reported by many others before. At least in my case I was able to track down the issue quite easily since it was working fine the day before. I had installed mesa-libOpenCL and libclc. Once I uninstalled those packages, makemkv stopped hanging. So apparently makemkv has a bad interaction with the default OpenCL libraries on Fedora.
My system: Linux [hostid] 4.0.4-202.fc21.x86_64 #1 SMP Wed May 27 22:28:42 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
I hope this helps someone else.
Solution to makemkv hang
Re: Solution to makemkv hang
Just a wild hunch, have you tried to do a "yum update OpenCL" yet?
Always back it up.
Re: Solution to makemkv hang
Everything was up-to-date when I was testing this.