This bug eluded me during several days because there was another bug that already caused VS 2010 Beta 2 to hang , but finally a couple of days ago I realized that was seeing a different issue (no commandbarbutton involved in this new bug) and I was able to isolate and report it today: VS 2010 Beta 2 Bug: adding CommandBarPopup to CommandbarPopup causes VS to hang if CommandBarPopup was added to Toolbar before https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=507650 As I expressed some days ago , my feeling with VS 2010 so far (after four builds) is that once you patch your add-in to (somehow) bypass a bug, the add-in finds a new one. The (VB.NET) code to reproduce it is: Imports System Imports Microsoft.VisualStudio.CommandBars Imports Extensibility Imports EnvDTE Imports EnvDTE80 Public Class Connect