I'm having the darndest XML config file problem that I really need help with.  

I'm supporting a .NET 1.1 desktop application with its own config file, and
I implement IConfigurationSectionHandler so I can have a custom config
section in my config file.  The IConfigurationSectionHandler.Create method
just returns the 'section' XmlNode back to the consumer.  The config file
looks kind of like this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<section name="MyConfigSettings" type="MyAssembly.ConfigReader, MyAssembly" />
</configSections>
<appSettings>
</appSettings>
<MyConfigSettings>
<ConfigSet zone="Test">
<add key="FirstKey" value="FirstValue"/>
<add key="SecondKey" value="SecondValue"/>
<add key="ThirdKey" value="ThirdValue"/>
</ConfigSet>
<ConfigSet zone="Integration">
<add key="FirstKey" value="FirstValue"/>
<add key="SecondKey" value="SecondValue"/>
<add key="ThirdKey" value="ThirdValue"/>
</ConfigSet>
</MyConfigSettings>
</configuration>

Then I've got this section of code that looks like this:

   Public Shared Sub SetConfigZone(ByVal Zone As String)

       Dim debug As String

       Try
           debug &= "Checking Zone variable " & Environment.NewLine

           If (Zone Is Nothing) Then
               MessageBox.Show("Zone variable passed in is nothing")
           End If

           debug &= "Getting XmlNode from config file " & Environment.NewLine
           Dim parent As XmlNode =
ConfigurationSettings.GetConfig("MyConfigSettings")

           debug &= "Checking parent variable " & Environment.NewLine
           If (parent Is Nothing) Then
               Throw New ConfigurationException("Unable to locate the
custom configuration section MyConfigSettings.  Please check your config
file.")
           End If

           MessageBox.Show(parent.OuterXml)

           debug &= "Beginning loop through nodes " & Environment.NewLine
           For Each node As XmlNode In parent.ChildNodes
               MessageBox.Show(node.OuterXml)
               debug &= "Inspecting Node's zone attribute... " &
Environment.NewLine
               If (node.Attributes("zone").Value = Zone) Then
                   debug &= "Correct node found... " & Environment.NewLine
                   debug &= "Creating new NameValueCollection... " &
Environment.NewLine
                   ConfigCommon.m_ConfigSettings = New NameValueCollection
                   debug &= "Looping through 'add' subnodes... " &
Environment.NewLine
                   For Each subNode As XmlNode In node.SelectNodes("add")
                       debug &= "Getting subnode's 'key' value... " &
Environment.NewLine
                       
ConfigCommon.m_ConfigSettings.Add(subNode.Attributes("key").Value,
subNode.Attributes("value").Value)
                   Next
                   Return
               End If
           Next
       Catch ex As Exception
           MessageBox.Show(debug, "Our debug message")
           MessageBox.Show(ex.ToString(), "Our error message")
       End Try

       'If we get this far, we haven't found our configuration section
       Throw New ConfigurationException("Unable to locate configuration
zone " & Zone)

   End Sub

So here's my problem.  This code has been working just great for the last
six to nine months, but all of a sudden about two weeks ago all of the new
machine builds our desktop group puts out fail at the following line:

               If (node.Attributes("zone").Value = Zone) //fails on first
run through

On new machines, it's producing a NullReferenceException.  But when I take
the exact same code and run it on anyone else's machine, it works just fine.  
In fact, you'll notice that I added a lot of little debugs and
MessageBox.Show statements in there to try to pinpoint it.  When I run the
code on my machine, I notice that the MessageBox.Show(node.OuterXml) produces
the first node.  When I run this on a newly built machine, the
MessageBox.Show produces an empty string.  

My question is:  what is missing from these new builds that was in the old
builds?  I think I've ruled out different versions of the .NET framework.  
Even if this was a breaking change in .NET 2.0, I tried forcing the .NET
Framework in the config file to 1.1 and still got the same error.  And the
users definitely have the .NET 1.1 Framework.  

Please help.  

Thanks.