After port localforward,SFTP failed [1]

I forward the port 22 of remote sftp server to localhost and send sftp connection request ,following information appears;

STATUS:> Session started...
STATUS:> Resolving the host 'localhost'...
STATUS:> Connecting to the server 'localhost'...
STATUS:> Version exchange initiated...
STATUS:>

In the left-down corner of the opened session window I could see:

Could not rename user key.....


Is there anyone could help me,actually serveral days ago I suucessfully connected to that server like this.

Program Ver. : Xftp 3.0

SFTP should work through forwarded tunnel.

To further investigate this problem, please send us the following information?

1. Name/version of the remote host
2. Send us the SSHd configuration file: /etc/ssh/sshd_config file
3. Can you connect to the server without using port forwarding?
4. Everything you see in the log window (View > log window) after connection fails



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Technical Support