Insert xml data into SQL server via SqlBulkCopy with powershell (casting error)

This might be move useful to test this issue:

Here is an example of the xml I want to insert:

   <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
        <System>
                <Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-a5ba-3e3b0328c30d}"/>
                <EventID>4625</EventID>
                <Version>0</Version>
                <Level>0</Level>
                <Task>12544</Task>
                <Opcode>0</Opcode>
                <Keywords>0x8010000000000000</Keywords>
                <TimeCreated SystemTime="2013-07-19T19:27:14.515Z"/>
                <EventRecordID>39751424</EventRecordID>
                <Correlation/>
                <Execution ProcessID="568" ThreadID="1608"/>
                <Channel>Security</Channel>
                <Computer>myserver.mydom.com</Computer>
                <Security/>
        </System>
        <EventData>
                <Data Name="SubjectUserSid">mysid</Data>
                <Data Name="SubjectUserName">myuser</Data>
                <Data Name="SubjectDomainName">mydom</Data>
                <Data Name="SubjectLogonId">0x5ca73f</Data>
                <Data Name="TargetUserSid">S-1-0-0</Data>
                <Data Name="TargetUserName">myuser2</Data>
                <Data Name="TargetDomainName">mydom</Data>
                <Data Name="Status">0xc000006d</Data>
                <Data Name="FailureReason">%%2313</Data>
                <Data Name="SubStatus">0xc000006a</Data>
                <Data Name="LogonType">2</Data>
                <Data Name="LogonProcessName">seclogo</Data>
                <Data Name="AuthenticationPackageName">Negotiate</Data>
                <Data Name="WorkstationName">myserver</Data>
                <Data Name="TransmittedServices">-</Data>
                <Data Name="LmPackageName">-</Data>
                <Data Name="KeyLength">0</Data>
                <Data Name="ProcessId">0x3e8</Data>
                <Data Name="ProcessName">C:\Windows\System32\svchost.exe</Data>
                <Data Name="IpAddress">::1</Data>
                <Data Name="IpPort">0</Data>
        </EventData>
    </Event>

I get the following error when trying to insert data into sql via the following script:

    $SQLDBName = 'test'
    $SQLServer = 'mysrv,1433'
    
    #Open connection to sql DB
    $connectionString = "Server = $SQLServer;Integrated Security=true;Initial Catalog=$SQLDBName;"
    $SQLConnection = new-object ("Data.SqlClient.SqlBulkCopy") $connectionString
    $SQLConnection.DestinationTableName = "ForwardedEvents"
    
    #create columns for datatable and set their types
    $columns = @()
    $columns +=  #Order MUST match that of the DB
    (New-Object System.Data.DataColumn -ArgumentList @("SystemTime"        , [System.string]         )),  
    (New-Object System.Data.DataColumn -ArgumentList @("EventLogXML"       , [System.Xml.XmlNode] ))
    
    #build datatable for bulk insert
    $dt = New-Object System.Data.DataTable
    $columns | %{$dt.Columns.add($_) | Out-Null}
    
    $row = $dt.NewRow() #Create row
    $row.Item("SystemTime")         = "This string get inserted fine"
    $row.Item("EventLogXML")        = [xml](cat C:\test\4625_forForums.xml)
    $dt.Rows.Add($row) #add row to table
    
    #insert into DB and close connection
    $SQLConnection.WriteToServer($dt)
    $SQLConnection.close()

Error: Exception calling "WriteToServer" with "1" argument(s): "Specified cast is not valid."



Really appreciate any assistance, thanks in advance.