While connecting to my web server using filezilla, i am getting this error:

Status: Resolving address of ftp.mysite.org.in
Status: Connecting to 199.199.199.18:21...
Status: Connection established, waiting for welcome message...
Response:   220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
Response:   220-You are user number 1 of 150 allowed.
Response:   220-Local time is now 17:58. Server port: 21.
Response:   220-This is a private system - No anonymous login
Response:   220-IPv6 connections are also welcome on this server.
Response:   220 You will be disconnected after 5 minutes of inactivity.
Command:    AUTH TLS
Response:   234 AUTH TLS OK.
Status: Initializing TLS...
Error:  GnuTLS error -9: A TLS packet with unexpected length was received.
Status: Server did not properly shut down TLS connection
Error:  Could not connect to server

I use a cradlepoint CTR35 wifi router to connect to the wired internet connection. When i connect to the same server without this router, the connection works flawlessly.

So i guess there is some problem with my router firewall settings, but i dont know what! Can somebody help me out please?

Note: The server requires EXPLICIT FTP OVER TLS and does not work with plain FTP sessions. And i can connect to other servers using plain FTP with the router in between.