We just created a form and when submitting the initial form, we get an "Error 500" message returned instead of the form submission.

In the reporting, the form shows as In Process on the "Start" step.

The event log shows an error as well for each attempt to submit:

6/30/2015 12:24:10 AM
Message: '' is an invalid expanded name.
Stack trace:    at System.Xml.Linq.XName.Get(String expandedName)
   at Laserfiche.Forms.Routing.VariableXMLGenerator.CreateElementFromMember(member mem, Nullable`1 repeatId)
   at Laserfiche.Forms.Routing.VariableXMLGenerator.CreateDummyXmlElement(member mem, Int32 attribute_id, Nullable`1 repeatId, String member_path)
   at Laserfiche.Forms.Routing.VariableXMLGenerator.ValidateEntity(XElement entityElement, entity entityToValidate, String memberPath, List`1 attributePool)
   at Laserfiche.Forms.Routing.VariableXMLGenerator.GenerateXml(Int32 bpInstanceId, Nullable`1 formId, cf_user_snapshot initiator, Nullable`1 submissionId, Nullable`1 initiatedTime)
   at Laserfiche.Forms.Routing.VariableXMLGenerator.GetLatestDataBySubmission(Int32 mainInstanceId, Int32 formId, Nullable`1 submissionId, cf_user_snapshot initiator, Nullable`1 initiatedTime)
   at Laserfiche.Forms.Routing.RoutingContext.InitializeProcessInstance(Int32 refMainProcInstId)
   at Laserfiche.Forms.Routing.RoutingContext.InitializeRoutingContext(Int32 procWorkerInstId, Int32 processId, Int32 boundaryEventStepId, SubmissionDataSet inputData, Int32 mainProcInstId, Int32 refMainProcInstId)
   at Laserfiche.Forms.Routing.RoutingDispatcher.RunProcess(Int32 processWorkerInstanceId, Int32 processId, Int32 boundaryEventStepId, SubmissionDataSet inputData, Int32 mainProcessInstanceId, Int32 refMainProcessInstanceId, Int32 lastSubmissionId)
   at Laserfiche.Forms.Routing.RoutingEngineService.RunRouting(RoutingRequestParameters requestParam)
   at Laserfiche.Forms.Routing.RoutingEngineService.<>c__DisplayClass1.<StartRouting_Async>b__0()

Any ideas where the form is going wrong?