I have noticed that it is possible for a control to be orphaned i.e. it is listed in the properties drop down box but selecting it in the drop down box does not cause it to be highlighted in design view.
If you open for example the Form1.Designer.vb file the orphan control does not have a parent control i.e. nowhere within the code is there a Me.<name>.Controls.Add(Me.OrphanControlName)
I have been hacking around a fairly complex form now (couple of hundred controls on it) and discovered I had run up probably about 30 or so orphaned controls, the only way I have found to remove them is by directly editing the Form1.Designer.vb file itself.
Cheers
Si