I am randomly getting InvalidCastException when showing FolderBrowserDialog and also many clients have reported this. I have not been able to find anything relevant on the internet. Does anyone know what causes this/how to fix this? My code: using (FolderBrowserDialog fbd = new FolderBrowserDialog()) { fbd.ShowNewFolderButton = false; if (fbd.ShowDialog() == DialogResult.OK) Stack trace: Error: System.InvalidCastException: 'Unable to cast object of type 'System.__ComObject' to type 'IMalloc'.'. Stack trace: at System.Windows.Forms.UnsafeNativeMethods.Shell32.SHGetMalloc(IMalloc[] ppMalloc) at System.Windows.Forms.FolderBrowserDialog.GetSHMalloc() at System.Windows.Forms.FolderBrowserDialog.RunDialog(IntPtr hWndOwner) at System.Windows.Forms.CommonDialog.ShowDialog(IWin32Window owner) at System.Windows.Forms.CommonDialog.ShowDialog() EDIT: Additional information: I have been able to reproduce this only when running in VS2008 debugger. When running out of debugger, it happens only very rarely (happened once or twice in 6 months) on my 64 bit Windows 7 and goes away after restart. The clients are certainly not running the app in debugger so it is surely reproducible out of debugger.