Getting this error message today:
Engine RunWorkflow: System.Workflow.ComponentModel.Compiler.WorkflowValidationFailedException: The workflow failed validation. at System.Workflow.Runtime.WorkflowDefinitionDispenser.ValidateDefinition(Activity root, Boolean isNewType, ITypeProvider typeProvider) at System.Workflow.Runtime.WorkflowDefinitionDispenser.LoadRootActivity(Type workflowType, Boolean createDefinition, Boolean initForRuntime) at System.Workflow.Runtime.WorkflowDefinitionDispenser.GetRootActivity(Type workflowType, Boolean createNew, Boolean initForRuntime) at System.Workflow.Runtime.WorkflowRuntime.InitializeExecutor(Guid instanceId, CreationContext context, WorkflowExecutor executor, WorkflowInstance workflowInstance) at System.Workflow.Runtime.WorkflowRuntime.Load(Guid key, CreationContext context, WorkflowInstance workflowInstance) at System.Workflow.Runtime.WorkflowRuntime.GetWorkflowExecutor(Guid instanceId, CreationContext context) at System.Workflow.Runtime.WorkflowRuntime.InternalCreateWorkflow(CreationContext context, Guid instanceId) at System.Workflow.Runtime.WorkflowRuntime.CreateWorkflow(Type workflowType, Dictionary`2 namedArgumentValues, Guid instanceId) at Microsoft.SharePoint.Workflow.SPWinOeHostServices.Send(SPWinOeWorkflow winoeworkflow, SPWorkflowEvent e) at Microsoft.SharePoint.Workflow.SPWinOeEngine.RunWorkflow(Guid trackingId, SPWorkflowHostService host, SPWorkflow workflow, Collection`1 events, TimeSpan timeOut)
If your workflow uses validation rules it might be:
1) A problem with your validation rules, restart Visual Studio re-compile are any errors picked up?
2) Missing the .net 3.5 workflow targets in your project file see: http://blog.hhebnes.no/post/WSPBuilder-Workflow-Failed-On-Start.aspx
Edward Wilde 