Exception calling "Add" with "1" argument(s): "This row already belongs to this table."

Good afternoon Powershell.com !

I am trying to automate some paper based processes using Powershell. We already had in place a Powershell solution where the output was an Excel Spreadsheet, but for planning for the future we felt that a CSV output was easier to work with than Excel.

What we are doing is pretty basic, we are reaching out to the owners of groups in AD, specified in a text file. For each group listed, we're looping through and adding the items to the table. Here's the problem, I am still very new to Powershell and am having issues looping through the 'for each' statements cleanly.

I am experiencing the following error:

    Exception calling "Add" with "1" argument(s): "This row already belongs to this table."
    At line:77 char:17
    + $table2.Rows.Add <<<< ($row2)
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : DotNetMethodException

I feel it's appropriate to share the code I am working with:

import-module activedirectory
$strGroupList = get-content "C:\Users\MYUSERNAME\Documents\Group Audit\audit.txt"
$strDate = Get-Date

foreach ($strGroup in $strGroupList)
{
$strGroupMember = Get-aduser -Identity $Group -property description
$tabName = "GroupAuditTable"

#Create the Table Object
$table = New-Object system.Data.DataTable "$tabName"
$table2 = New-Object system.Data.DataTable "$tabName2"

#define columns for row 1
$col1 = New-Object system.Data.DataColumn $strGroup,([string])
$col2 = New-Object system.Data.DataColumn $strDate,([string])

#define columns for row 2
$col3 = New-Object system.Data.DataColumn Name,([string])
$col4 = New-Object system.Data.DataColumn Description, ([string])
$col5 = New-Object system.Data.DataColumn NetworkID, ([string])
$col6 = New-Object system.Data.DataColumn Nested, ([string])

#Add the columns to row 1
$table.columns.add($col1)
$table.columns.add($col2)

#Add the columns to row 2
$table2.columns.add($col3)
$table2.columns.add($col4)
$table2.columns.add($col5)
$table2.columns.add($col6)

#create a row
$row = $table.NewRow()
$row2 = $table2.NewRow()

#create an additional row for the titles of columns
$rowTitles = $table.NewRow()
$rowTitles2 = $table2.NewRow()

$strGroupDetails = Get-ADGroupMember -identity $strGroup 
foreach ($Group in $strGroupDetails)
    {
##########################################################################  Check for nested groups        
        if($Group.ObjectClass -eq "group")
        {
        $strGroupDetails = Get-ADGroupMember -identity $Group #-Recursive
        $strNestedGroupName = $Group.name
##########################################################################  List members of nested groups
        foreach($strNestedGroup in $strGroupDetails)
            {
            #$strNestedGroupName = $Group.name
            $strGroupMember = Get-aduser -Identity $StrNestedGroup -property description

            $row2.Name = $strGroupMember.name
            $row2.Description = $strGroupMember.description
            $row2.NetworkID =  $strGroupMember.SamAccountName
            $row2.Nested = "(From NESTED GROUP:  " + $strNestedGroupName
            $table2.Rows.Add($row2)
            }
        }

        else
        {
#enter data into row 2

$row2.Name = $strGroupMember.name
$row2.Description = $strGroupMember.description
$row2.NetworkID =  $strGroupMember.SamAccountName
$row2.Nested = "Not Nested"

#Add the row to the table
$table.Rows.Add($row)

#Add the row to the second table
$table2.Rows.Add($row2)

#Display the table
$table | format-table -AutoSize
$table2 | format-table -AutoSize
}




}

}
$tabCsv = $table | export-csv C:\Users\MYUSERNAME\Desktop\Audit\GroupAudit.csv -noType
$tabCsv2 = $table2 | export-csv C:\Users\MYUSERNAME\Desktop\Audit\GroupAudit_2.csv -noType

That's it, pretty basic stuff.

The error is on line #77:

$table2.Rows.Add($row2)

This worked before I stuck the 'Nested Groups' For Each loop in there, and I am just puzzled as to why that would break it, unless I am missing something obvious here. When I remove this:

foreach ($Group in $strGroupDetails)
    {
##########################################################################  Check for nested groups        
        if($Group.ObjectClass -eq "group")
        {
        $strGroupDetails = Get-ADGroupMember -identity $Group #-Recursive
        $strNestedGroupName = $Group.name
##########################################################################  List members of nested groups
        foreach($strNestedGroup in $strGroupDetails)
            {
            #$strNestedGroupName = $Group.name
            $strGroupMember = Get-aduser -Identity $StrNestedGroup -property description

            $row2.Name = $strGroupMember.name
            $row2.Description = $strGroupMember.description
            $row2.NetworkID =  $strGroupMember.SamAccountName
            $row2.Nested = "(From NESTED GROUP:  " + $strNestedGroupName
            $table2.Rows.Add($row2)
            }
        }

        else
        {
#enter data into row 2

Things work as expected, what am I missing?