Based on the information supplied by Marcus Kramer, I found the following description of a "feature" regarding the Tab Control Alignment attribute in the MSDN library:
http://msdn.microsoft.com/en-us/library/system.windows.forms.tabcontrol.alignment.aspx[
^]
This lead me to a Windows API call which selects and disables (by selecting no theme) themes for controls:
SetWindowTheme Function(
^)
I found that this solution must be applied to each afflicted tab control:
Public Class Form1
Public Declare Unicode Function SetWindowTheme Lib "uxtheme.dll" (ByVal hWnd As IntPtr, _
ByVal pszSubAppName As String, ByVal pszSubIdList As String) As Integer
Private Sub Form1_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
Dim sb As String = String.Empty
Dim v As String = String.Empty
If Environment.OSVersion.Version.Major = 5 And _
Environment.OSVersion.Version.Minor = 1 Then
SetWindowTheme(Me.TabControl1.Handle, " ", " ")
End If
End Sub