If you do anything "out of the ordinary" in your UserControl or Form derived classes in Visual Studio 2005, let me introduce you to a little snippet that will probably save you lots of headaches:

if ( DesignMode ) return;

or, its equally useful counterpart

if(!DesignMode){
	doStuff();
}

Now, the "out of the ordinary" thing I was doing was...hooking up an instance EventHandler using a static property that exposes a Form derived class in an OnLoad override. What? I know, not the clearest situation, and probably one that could use a boatload of refactoring, but it works. In short, if you are having designer problems in Visual Studio 2005, it may be worth it to sit back for a bit and think about what introduced the designer error. Prime candidates are constructors and OnLoad overrides that use static methods for functionality. This code didn't allow me to view the designer of a different form:

public override void OnLoad(EventArgs e){
	AppManager.ConcreteEditorForm.NewPostCreated += new EventHandler(HandleNewPost);
}

while this one would:

public override void OnLoad(EventArgs e){
	if( DesignMode ) return;
	AppManager...
}