IHttpAsyncHandler is hanging up after 3-4 requests

 I am writing a ASP.NET based REAL TIME COMET server. But project is now 98% complete. But there is 1 mysterous thing I can not find anywhere.
Actual code is quite long, so to reproduce the problem I wrote following simple handler.
 
    public class CometHandler : IHttpAsyncHandler
    {           
        #region IHttpAsyncHandler Members

        public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
        {     
            // TESTING
            AsyncResultWrapper ar = new AsyncResultWrapper(cb, extraData);

       &n ...