I am having the exact same problem Matt had in August below. Media 100 2.1.8 keeps crashing when trying to open on macOS Sierra 10.12.6. Please let me know how to solve this issue. Tried uninstalling and reinstalling the application several times with no change.
I have not yet installed High Sierra. This is just on Sierra (10.12.6). I installed Media 100 2.1.8 fresh and was opening some projects and making sure they worked. Everything was working for awhile when the system crashed. Then, the application would no longer open at all. Every time I tried and even with different projects, it wouldn't get past the opening screen before it crashed.
I tried running the uninstaller and reinstalling 2.1.8. Same thing happening. I also repeated that again and trashed my preferences - same result. I ended up re-imaging the machine I was on and installing 2.1.8 again so I am up and running but I am worried this is only temporary until it crashes again. It would be helpful to know how to fix this issue in the future if it occurs and what files need to be changed or deleted in order to regain functionality.