www.makemkv.com

MakeMKV:

Just wanted to let you know that as of today, current versions of FireFox and MakeMKV for OSX will cause MakeMKV to have the "Fatal Error, program will now exit" error randomly while FireFox is running.

When firefox is NOT running, MakeMKV is stable.

Not a programmer, so no idea why. But I imagine the information is useful for you to be aware of

Verified bad with:

Firefox for OSX V3.6.3
MakeMKV for OSX 1.5.4 beta

For what it's worth, this version of FireFox seems pretty buggy under OSX. I've had quite a few firefox crashes
(Running Safari does not seem to cause any problems for MakeMKV)