Unity 5.2 hangs upon running compiled game

I've just upgraded from Unity 5.1.3 to 5.2. My application was running fine, and the upgrade seemed to complete without issues. The project is now reporting as being a 5.2 project.

However, whenever I test play the game in the editor Unity just completely hangs with the play button semi pressed (grey not blue). I have to end task Unity to get out of this.

I can actually build my application without error. Running the compiled executable then hangs on a grey screen, and the process maxes out a core. This again goes until I force an end task.

The event log shows this:

   <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
     <System>
       <Provider Name="Application Hang" /> 
       <EventID Qualifiers="0">1002</EventID> 
       <Level>2</Level> 
       <Task>101</Task> 
       <Keywords>0x80000000000000</Keywords> 
       <TimeCreated SystemTime="2015-09-11T21:41:03.000000000Z" /> 
       <EventRecordID>94705</EventRecordID> 
       <Channel>Application</Channel> 
       <Computer>Cerberus</Computer> 
       <Security /> 
     </System>
     <EventData>
       <Data>******.exe</Data> 
       <Data>5.2.0.38013</Data> 
       <Data>1a60</Data> 
       <Data>01d0ecda70c54b67</Data> 
       <Data>68</Data> 
       <Data>F:\******.exe</Data> 
       <Data>ca4373ca-58cd-11e5-841c-5cf370639748</Data> 
       <Data /> 
       <Data /> 
       <Binary>55006E006B006E006F0077006E0000000000</Binary> 
     </EventData>
   </Event>

That binary data is a UTF encoded string reading "Unknown".

Does anyone know why this might be happening?