error sending data to the server. SymbianOS error -1

[dihex]

I have an application that sends data to a servlet. It has been working fine on the WTK emulator.

When I run it on a nokia 6630 (this is the only phone i have tried it on) I get the following error:

=====================
Error connecting to the server:

SymbianOS error = -1:
General:
System error
=====================

my code to connect is as follows:

<snip>
        HttpConnection conn = null;

        try
        {
            progDisplay("Connecting to the server..." );
            conn = (HttpConnection)Connector.open( url );
            sendData(conn, data);
        }
         catch( IOException e )
        {
            progDisplay("Error connecting to the server:" + "\n" + e.getMessage());
        }

<snip>


    private void sendData(HttpConnection conn, byte[] data)  throws IOException
    {
        conn.setRequestMethod( HttpConnection.POST );
        conn.setRequestProperty("Content-Language", "en-US" );
        conn.setRequestProperty("Accept", "application/octet-stream" );
        conn.setRequestProperty("Connection", "close" );
        conn.setRequestProperty("Content-Length", Integer.toString( data.length ) );

        OutputStream os = conn.openOutputStream();
        os.write( data );
        os.close();
    }

I got it to output progress information when in the sendData() method and it stopped between os.write( data ); and os.close(); By that i mean i got it to print out a message after every step in that method, the last message that got printed was just after os.write( data );

Why would there be a problem closing the stream??

Any help would be much appreciated.