Just started happening after the last upgrade. Here is the VS activity log:
System.Collections.Generic.KeyNotFoundException: key at Microsoft.VisualStudio.Utilities.PropertyCollection.GetProperty(Object key) at Mindscape.VisualSass.Integration.Intellisense.SignatureHelpSource.AugmentSignatureHelpSession(ISignatureHelpSession session, IList1 signatures) at Microsoft.VisualStudio.Language.Intellisense.Implementation.SignatureHelpSession.Recalculate() at Microsoft.VisualStudio.Language.Intellisense.Implementation.SignatureHelpSession.Start() at Microsoft.VisualStudio.Language.Intellisense.Implementation.SignatureHelpBroker.TriggerSignatureHelp(ITextView textView) at Microsoft.Web.Editor.CompletionController.ShowSignature(Boolean autoShown) at Microsoft.Web.Editor.CompletionController.OnPostTypeChar(Char typedCharacter) at Microsoft.Less.Editor.LessCompletionController.OnPostTypeChar(Char typedCharacter) at Microsoft.Web.Editor.TypingCommandHandler.HandlePostTypeChar(Char typedChar) at Microsoft.Web.Editor.TypingCommandHandler.PostProcessInvoke(CommandResult result, Guid group, Int32 id, Object inputArg, Object& outputArg) at Microsoft.Web.Editor.Controller.Invoke(Guid group, Int32 id, Object inputArg, Object& outputArg) at Microsoft.Web.Editor.Controller.Invoke(Guid group, Int32 id, Object inputArg, Object& outputArg) at Microsoft.VisualStudio.Web.Editor.CommandTargetToOleShim.Exec(Guid& guidCommandGroup, UInt32 commandID, UInt32 commandExecOpt, IntPtr variantIn, IntPtr variantOut) at Microsoft.VisualStudio.Editor.Implementation.CommandChainNode.InnerExec(Guid& pguidCmdGroup, UInt32 nCmdID, UInt32 nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut) at Microsoft.VisualStudio.Editor.Implementation.CommandChainNode.Exec(Guid& pguidCmdGroup, UInt32 nCmdID, UInt32 nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut) at Mindscape.VisualSass.Integration.Intellisense.Controller.Exec(Guid& pguidCmdGroup, UInt32 nCmdID, UInt32 nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut) at Microsoft.VisualStudio.Editor.Implementation.CommandChainNode.InnerExec(Guid& pguidCmdGroup, UInt32 nCmdID, UInt32 nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut) at Microsoft.VisualStudio.Editor.Implementation.VsTextViewAdapter.Exec(Guid& pguidCmdGroup, UInt32 nCmdID, UInt32 nCmdexecopt, IntPtr pvaIn, IntPtr pvaOut) at Microsoft.VisualStudio.Editor.Implementation.VsKeyboardFilter.SendCommand(Guid cmdGroup, UInt32 cmdID, Object inParam) at Microsoft.VisualStudio.Editor.Implementation.VsKeyboardFilter.TextInput(TextCompositionEventArgs args) at Microsoft.VisualStudio.Text.Editor.Implementation.KeyProcessorDispatcher.<DispatchTextInputEvents>b__0(KeyProcessor p, TextCompositionEventArgs args) at Microsoft.VisualStudio.Text.Editor.Implementation.KeyProcessorDispatcher.<>c__DisplayClass1e1.b__1a() at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.CallExtensionPoint(Object errorSource, Action call)
