Host is not communicating for more than ....

Hi,
I can connect to my remote linux machine with VNC and putty. However I don't know why I can not via winscp. How can I debug? I see this message "Host is not communicating for more than X seconds"

Can you post a log file?

It seems there was a transient problem with our main server that didn't establish a connection. Anyway thanks.

Sorry that post was mine. It was my fault to post without login!