ASP.NET 4 errors and lockups

We've been getting lockups with 3.7/1.4 since we've got it.

I got in our local reseller to have a look at it and couldn't replicate it, but we've move to production and it's still happening.

I think I'm getting closer to the problem.   Looking at the windows logs when it's happening I'm getting multiple ASP.NET 4 errors.

When saving or even trying to login to the rest manager I'm getting lockups in the interface which affects all users.   We've moved machines so it must be a site configuration issue (or possibly proxy issues).

Anyway I'm getting the below error while the lockups are occurring.... Any ideas? 

 

An unhandled exception occurred and the process was terminated.

Application ID: /LM/W3SVC/1/ROOT/Geocortex/Essentials/REST

Process ID: 10000

Exception: System.NullReferenceException

Message: Object reference not set to an instance of an object.

StackTrace:    at Geocortex.Essentials.Configuration.Models.GroupLayerConfig.ConfigureGroupLayer(GroupLayer groupLayer, Site site)

 

   at Geocortex.Essentials.Configuration.Models.GroupLayerConfig.ConfigureLayer(Layer layer, Site site)

 

   at Geocortex.Essentials.Configuration.Models.GroupLayerConfig.ConfigureGroupLayer(GroupLayer groupLayer, Site site)

 

   at Geocortex.Essentials.Configuration.Models.GroupLayerConfig.ConfigureLayer(Layer layer, Site site)

 

   at Geocortex.Essentials.Configuration.Models.LayerBaseConfig.ToBusinessObject(MapService mapService, GroupLayer parentLayer, Site site)

 

   at Geocortex.Essentials.Configuration.Models.MapServiceBaseConfig.ConfigureMapService(MapService mapService, Site site)

 

   at Geocortex.Essentials.Configuration.Models.MapServiceConfig.ConfigureMapService(MapService mapService, Site site)

 

   at Geocortex.Essentials.Configuration.Models.MapServiceBaseConfig.ToBusinessObject(Site site)

 

   at Geocortex.Essentials.Configuration.Models.MapBaseConfig.<>c__DisplayClass5.<ConfigureMap>b__1()

 

   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)

 

   at System.Threading.ExecutionContext.runTryCode(Object userData)

 

   at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)

 

   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)

 

   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)

 

   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)