DesignTime error message (Winforms)

I am upgrading my project to 3.3.0.0 version. When I create new form, drop FrameBarManagment on it and configure some BarItems for it, I get [''BarTypeConverter'' is unable to convert ''Syncfusion.Windows.Forms.Tools.XPMenus.Bar'' to ''System.ComponentModel.Design.Serialization.InstanceDescriptor''.] error message when trying to save a form. What would cause such error? Thanks Konstantin

Loader.
Up arrow icon