Forms :: ProcessTabKey Method - One Of ComboBoxes Skips

I'm trying to detect when the tab key was pressed and intercept it in certain cases. Since the form I'm working with has many fields, I've tried overriding ProcessTabKey so that I don't have a separate sub for each control. However, I've found that after adding a simple ProcessTabKey method, each time I press tab it skips one of the combo boxes. In order to duplicate the situation, using Visual Basic Express 2008, create a new Windows Forms project and add 5 combo boxes to the form - allowing each to automatically get an incrementing TabIndex.

Then add the following code the form:
Public Class Form1
Protected Overrides Function ProcessTabKey(ByVal forward As Boolean) As Boolean
MyBase.ProcessTabKey(forward)
End Function
End Class

Now when you run the project, you'll see that each time you press tab it skips one of the combos.