SFTP Failed---Request for subsystem 'sftp' failed on channel 0

Hi,
While I am trying SFTP my machine to another unix machine ,
it was working fine till 10 min back.
But now i am getting the below error
"Request for subsystem 'sftp' failed on channel 0"

Could you please someone help me to solve or analyise the root cause...

Cheers:b:,
Mahiban