Copying files from remote side failed. Transfer complete.

Hi,

Please find below the details:
I have developed a File Transfer solution in Microsoft SQL Server Integration Services.
I first generate a text file with the script with instructions. Then I call the WinSCP executable with the script file.
It copies a zip file i.e generated everyday of the syntax 'name20130108.zip' from SFTP location to local then copies it to FTP or SFTP destination with a separate script.
WinSCP version: 5.0.8 (Build 2438)
Yesterday the copy from SFTP location to local machine failed. When I tried copying the file manually using the GUI, it gave me the error "Copying files from remote side failed. Transfer complete." even though the file gets copied. Through scripting it is failing because of the dialog box that comes.
Could you please tell me what could be the possible reason. Although, it is happening for yesterday's file only, if I copy day before yesterday's file using GUI, it gets copied without any hassle. I'll give you an update tomorrow if it fails for today's file.
I have tried to include as much information as I can.

First, please upgrade.
If the problem persists, please attach a full log file showing the problem (using the latest version of WinSCP).