Wierd Tabstrip webcontrol

[Patirck Ige]

I get error "can't move focus ot the control becuase it is invisible,not
enabled,or of type"
If i set Autopostback = TRUE"
And do
If tsHoriz.SelectedIndex = 0 Then
tsHoriz.Items(0).Enabled = True
tsHoriz.Items(1).Enabled = True
tsHoriz.Items(2).Enabled = True
tsHoriz.Items(3).Enabled = True
tsHoriz.Items(4).Enabled = False
End If
Which its just disabling the 4th TAB if the Tabstrip index = 0 .(The
tabstrip index starts from 0)
Any ideas