v4.2 Brought Work to Grinding Halt

Just upgraded to v4.2 from v4.1.3 on a Mac Pro (mid-2010) running 10.10.3 and it immediately brought all of my work to a grinding halt. Compressor immediately freezes entire computer after launch. Eager to use the new features but now stuck trying to find a way to revert back to v4.1.3 until the issue gets sorted.

Reviewer1987 about Compressor