Java memory leak when running on Red Hat but no memory leak on Mac OS X

I have a java webobjects app which is showing memory leak problems when running on Red Hat but we had no such problems when it was running on Mac OS X. The JVMs are similar.

Mac OS X 10.6.5 using java 1.6.0_22 64 bit from Apple Red Hat EL 5.0 using java 1.6.0_20 64 bit from Sun

I configured it to do a heap dump when it ran out of memory, and analysing this with the eclipse memory analyzer tool suggests that the problem is in a part of the code which creates a thread which sends an HTTP Request to a web service. The reason for creating the thread is to implement a timeout on the request because the web service is sometimes not available.

Does anyone have any ideas?

    WOHTTPConnection connection = new WOHTTPConnection(host, port);
    WORequest request = new WORequest(strMethod, strQuery, strHttpVersion, nsdHeader, content, null);

    WebServiceRequester theRequester = new WebServiceRequester(connection, request);
    Thread requestThread = new Thread(theRequester);
    requestThread.start();
    try {
            requestThread.join(intTimeoutSend);  //timeout in milliseconds = 10000
            if ( requestThread.isAlive() ) {
                requestThread.interrupt();
            }
    } catch(InterruptedException e) { 

    }
    requestThread = null;
    if(!theRequester.getTfSent()) {
           return null;
    }
    WOResponse response = connection.readResponse();

...

class WebServiceRequester implements Runnable {

    private WORequest theRequest;
    private WOHTTPConnection theConnection;
    private boolean tfSent = false;

    public WebServiceRequester(WOHTTPConnection c, WORequest r) {
        theConnection = c;
        theRequest = r;
    }

    public void run() {
        tfSent = theConnection.sendRequest(theRequest);
    }

    public boolean getTfSent() {
        return tfSent;
    }
}

EDIT: leaked class names as reported by eclipse memory analyzer tool:

1,296 instances of "java.lang.Thread", loaded by "<system class loader>" occupy 111,947,632 (43.21%) bytes.
1,292 instances of "er.extensions.eof.ERXEC", loaded by "java.net.URLClassLoader @ 0x2aaab375b7c0" occupy 37,478,352 (14.46%) bytes.
1,280 instances of "er.extensions.appserver.ERXRequest", loaded by "java.net.URLClassLoader @ 0x2aaab375b7c0" occupy 27,297,992 (10.54%) bytes.

I have heard that WOHTTPConnection is broken and shouldn't be used. WOHTTPConnection does not give you a reliable way of closing the connection. It is also unreliable in other ways.

The solution is to rewrite the code using Apache HttpComponents HttpClient