HI guys,

I get the following error when trying to add any workflow items to any of my forms:

[NullReferenceException: Object reference not set to an instance of an object.]
   Umbraco.Forms.Core.Common.ProviderCollection`1.(T , T ) +9
   System.FunctorComparer`1.Compare(T x, T y) +19
   System.Collections.Generic.ArraySortHelper`1.SwapIfGreaterWithItems(T[] keys, IComparer`1 comparer, Int32 a, Int32 b) +91
   System.Collections.Generic.ArraySortHelper`1.QuickSort(T[] keys, Int32 left, Int32 right, IComparer`1 comparer) +58
   System.Collections.Generic.ArraySortHelper`1.Sort(T[] keys, Int32 index, Int32 length, IComparer`1 comparer) +93

[InvalidOperationException: Failed to compare two elements in the array.]
   System.Collections.Generic.ArraySortHelper`1.Sort(T[] keys, Int32 index, Int32 length, IComparer`1 comparer) +330
   System.Array.Sort(T[] array, Int32 index, Int32 length, IComparer`1 comparer) +186
   System.Collections.Generic.List`1.Sort(Comparison`1 comparison) +108
   Umbraco.Forms.Core.Common.ProviderCollection`1.GetProviders() +448
   Umbraco.Forms.UI.Dialogs.editWorkflowDialog.Page_Load(Object sender, EventArgs e) +294
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +91
   umbraco.BasePages.BasePage.OnLoad(EventArgs e) +14
   System.Web.UI.Control.LoadRecursive() +74
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207

I did have two custom workflow items being developed, but I've now removed these from my source code and recompiled, and I still get this error even after recycling my app pool.

Any help/advice appreciated.

Best,

Benjamin