I don't know if this is limited to Infragistics, but we are having problems with doing things like right-clicking an Infragistics WinForms control to, say, open a custom designer which can sometimes take several minutes. Visual Studio blocks and the "Gear" shows during this time.
Is this a known problem?
I'm not sure that this is anything specific to Infragistics code, since there is generally not any performance-intensive code with loading designers. One case that I've come across in a solution with multiple forms/components is that Visual Studio tries to repopulate the Toolbox several times. You could try disabling this by navigating to Tools -> Options -> Windows Forms Designer -> General and set the AutoToolboxPopulate property to False.
-Matt