I've encountered a consistent problem starting up for the last couple weeks, most of the time when I start up the game it freezes or sometimes completely crashes. Maybe about 1 in 20 times the game starts up with seemingly no problem and I'm able to play to my heart's content until I quit and then the next time it's the same problem. It's completely inconsistent as well, I can't seem to reproduce the success conditions (including restarting steam, uninstalling/reinstalling KSP, and even restarting my laptop).
Comparing the log for a successful application launch vs a freeze vs a crash shows both the freeze and crash the log stops dead on loading audio. Specifically it just never reaches "Load(Audio): Squad/Sounds/editorLoop01", freezing/crashing just after "AppCanvas MASK: 3458764513820540928". It's always the same step causes the freeze/crash.
Just for fun I reverted to the last stable release in steam (1.0.5.1028) and the app launches just fine.
Clean install. KSP Version 1.1.2.1260
OS: Mac OS X 10.11.4
CPU: Intel(R) Core(TM) i7-3720QM CPU @ 2.60GHz (8)
RAM: 8192
GPU: NVIDIA GeForce GT 650M OpenGL Engine (1024MB)
https://dl.dropboxusercontent.com/u/34956216/KSP_failure.log
https://dl.dropboxusercontent.com/u/34956216/KSP_success.log