Transfer to remote site fails with Error 4

I have installed WinSCP 4.1.3 (Build 393) and setup my connection for SFTP. I get connected and can see the remote directory. But when I drag from local to remote I get Error code 4 for Request 6. The file name is created in the remote directory but size is zero.

What am I doing wrong?

TIA - Peter

Please read documentation. If that does not help, come back.