I have a WRVS4400N router setup at home with firmware V126.96.36.199 and ran into issues with SFTP.
Standard FTP traffic works just fine, but found any SFTP connection would fail trying to connect.
What I found was that IPS enabled for FTP, would cause the SFTP connection to fail when attempting to connect to the remote site.
I basically just disabled IPS for the FTP service.
This appears to be some sort of bug in the firmware and IPS.
Has anyone else run into this problem and is this a known issue with the WRVS4400N?