Coloring grid cells is irregular in IE - CSS issue

Hi, I use the following VB-Method for coloring some certain properties in the grid, e.g. the state column:

Dim tmpInn As Innovator = Me.getInnovator()
Dim i As Integer

For i=0 To Me.getItemCount()-1

  Dim bg_color_state As String
  Dim myCss As String
  Dim thisItem As Item = Me.getItemByIndex(i)
  'Choose color for 'State'
  Dim thisStatus As String = thisItem.getProperty("state","")
    '------
      Select (thisStatus)
          Case "Preliminary","In Review","In Change"
          bg_color_state = "#FFFFBB" 'light yellow
          Case "Released" 
          bg_color_state = "#90EE90" 'light green
          Case "Superseded","Obsolete" 
          bg_color_state = "#FFBBBB" 'light red
          Case Else
          bg_color_state = "" 'none
      End Select

  If bg_color_state <> "" Then
    myCss = ".state { background-color: " & bg_color_state & " }" & vbNewLine & ""
    thisItem.setProperty("css",myCss)
  End If
Next i
Return Me

Unfortunately, the coloring is not always performed correctly in IE. The color is fine, but the borders of the cell sometimes disappear. Is there a solution for this? It's not a big issue, but it does not look pretty. Best regards! Angela