IISExpress crashes with 0xc0000008 error

Occasionally when running my MVC4 site in VS2012 using IISExpress I get the following error and IISExpress stops:

iisexpress.exe: Managed (v4.0.30319)' has exited with code -1073741816 (0xc0000008) 'An invalid handle was specified

There is nothing in the event log for this and I cant find anything on the interweb.

I have some very vague theories:

• my site is using MEF a loads modules dynamically at startup. Maybe
  there is an occasional race condition so IIS cant open an assembly
  but my trace logs show that IIS is beyond that part of the startup
  cycle.
• it also has SignalR but apart from starting the hub it's not
  doing much yet. SignalR is pretty new and unproven but I've updated
  the latest RC2 version with the same result.

Oh and I also had the same error when using the VS Dev web server. I havent tried full IIS yet.

Anyone else go a clue ??

Thanks

UPDATE:

I fixed a couple of nuget references which seemed to stabalize things a bit, then this morning it happened again. The VS output window shows this:

'iisexpress.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.Mobile\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Web.Mobile.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'iisexpress.exe' (Managed (v4.0.30319)): Loaded 'C:\Users\peter.jones\AppData\Local\Temp\Temporary ASP.NET Files\root\a4aa93f7\dfa23a50\App_Web_rpzlbjhw.dll', Symbols loaded.
'iisexpress.exe' (Managed (v4.0.30319)): Loaded 'C:\Users\peter.jones\AppData\Local\Temp\Temporary ASP.NET Files\root\a4aa93f7\dfa23a50\App_Web_c1rjct4s.dll', Symbols loaded.
The program '[11072] iisexpress.exe: Managed (v4.0.30319)' has exited with code -1073741816 (0xc0000008) 'An invalid handle was specified'.

If there is some more useful logging somewhere I will happily provide it.

Cheers