Unity editor hangs on start up

I’m unable to start the Unity editor - it just hangs. This happens in OS X and Windows 8.1, on Unity 5.2.2, 5.2.4 and 5.3.1p3.

On OS X I’m getting this message in the editor log:

Native extension for OSXStandalone target not found

The workaround is to delete /Library and restart, but the rebuild takes around 5 hours each time as the project is 110GB. This is now happening every day, making working in Unity very difficult.

I opened a case (759598) a couple of weeks ago but I still haven't heard back from Unity support.

Any ideas from anyone?

 

To add to this, I also tried just deleting /ScriptAssemblies to force a recompilation without reimporting all the assets, but it didn’t help.

Also, there are no obvious errors in the shader compiler log.

 

Some more information:

• Software: Unity 5.3.1p3, OS X El Capitan 10.11.2
• Hardware: iMac Retina 5K 27", 4.0 GHz i7, 32GB, 3TB (128GB SSD), AMD Radeon R9 M395X (4GB VRAM)

 

It's just happened again (as it does every morning), and all I did was select a new window layout while compilation was in progress. Looks like I'll be doing something else for the next 5 hours.

A response from Unity would be nice. No-one else is seeing this issue on OS X since 5.2.x?

 

In my case it was hung on a semaphore- if you kill Unity while it's starting up, the semaphore can be left in a "bad state". The fix is to reboot your machine.