I have the same issue on my mac but it only occurs if I set the screen resolution to the native 2560x1440.
Reducing the screen res even to 2048x1152 works.
When at 2560x1440 I cannot load or create any save file without the game freezing and having to be force quit (the dock shows application not responding)
Gonqueasel - I would be interested to know if the game hanging is based on screen res for you as-well
Hope this helps.
KSP version 1.1.0
Running: Mac OSX 10.11.4 on a iMac (27-inch, Late 2012), 2.9 GHz Intel Core i5, 16 GB 1600 MHz DDR3, NVIDIA GeForce GTX 660M 512 MB
