FtpWebRequest doesn't work in parallel threads

I work with C# 2.0 VC2008.
I use a number of Background Workers for open multiply FTP Connections to same FTP Server. The connections are in an Active FTP Mode.
:thumbd: When I start 2 connections together, the first one is working properly and the second stops after the connection has been established good and waits for Data ( get data only after the first connection closed ).
:thumb: When I run two applications with one FTP Session for each, I haven't any problem.


This is a part of request code :

Code:

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// sPath =  "ftp://user_name:user_pass@server_address:21//path")
                FtpWebRequest request = (FtpWebRequest)WebRequest.Create( sPath ); 
                request.UsePassive = false;
                request.Proxy = null;
                request.Method = WebRequestMethods.Ftp.GetFileSize;

                this.curFTPState.FileName = Path.Combine(sPathTo, filename);
                this.curFTPState.FTPMethod = WebRequestMethods.Ftp.GetFileSize;
                this.curFTPState.Request = request;


                // Start the asynchronous request. 
                IAsyncResult result = (IAsyncResult)request.BeginGetResponse(new AsyncCallback(RespCallback), curFTPState);

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Does the FTP server in question allow multiple connections from the same IP?

Yes, actually same application, has run twice with one connection each, is connecting and getting data perfect. On specific server I can open only 2 connections simultaneously, because system limitation.