Since installing the Yosemite update MacHg 0.9.25 has been crashing a lot.
Starting MacHG or saving changes to a tracked file can be enough to trigger a crash. I've also experienced crashes when pulling, commiting, pushing and updating. This is happening on multiple Macs with existing MacHG installs. Usually I get a 'MacHg has quit unexpectedly' message while MacHG keeps running.
There is no 100% certain way to reproduce this but it does happen very frequently.