Our customer reported that Contour suddenly threw an "An item with the same key has already been added." exception, when viewing "Workflow" node for all of their forms. This happens on Umbraco 4.6.1 and Contour 1.1.6.

[ArgumentException: An item with the same key has already been added.]
   System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) +12679472
   Umbraco.Forms.Data.Storage.SettingsStorage.GetSettings(Guid id) +305
   Umbraco.Forms.Data.Storage.WorkflowStorage.GetAllWorkFlows(Form form) +343
   Umbraco.Forms.UI.Pages.editFormWorkflows.OnInit(EventArgs e) +752
   System.Web.UI.Control.InitRecursive(Control namingContainer) +133
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1970

I updated their testing environment to Umbraco 4.11.1 and Contour 3.0.1 (via the update), but the same error occurs.

Having a look in the database, table "UFSettings" for the faulty forms, each had 6 identical entries:
[Id]: 7DD14A5A-69A9-4706-81DD-47A20C994CD1 (guid for one of the faulty forms)
[Key]: "XPathOnSubmit"
[Value]: ""

I've tried to clear of 5 of these records (also all) and touched web.config/removed cookies, but it has no effect.

As a final solution, I will clear out the forms and ask the customer to create them once again, since it seems to be working. But if any of you knew a quickfix for getting the existing forms working again, that would of course be the best case scenario :-).