AS/400 FTP timing issue

I have below a log of a FTP communication issue that I would like someones opinion about. 
The below log shows at 2013-01-14-19.55.21.281284  that a CD command was issued.
Then at 2013-01-14-19.55.27.335028 the FTP response came back as CWD command successful.
Without entering another command, at 2013-01-14-19.55.27.557637 the FTP response was CD error which caused an application program to abort.
I do not know how to explain this except to guess it is a timing error. The sign on, CD, and FTP takes place with this same script all night long without issue and occasionally  this message pops up and causes the program to abort. 
I am at a loss. Can someone with FTP knowledge point me in the right direction to what might be happening?
 
 
2013-01-14-19.55.21.281178 Resp - 331 Password required for administrator.                     
2013-01-14-19.55.21.281208 Resp - 230 User administrator logged in.                            
2013-01-14-19.55.21.281284 Cmd  - CD 'WMUploads'                                               
2013-01-14-19.55.21.281318 Cmd  - NOOP                                                         
2013-01-14-19.55.27.334787 Resp - Windows_NT                                                    
2013-01-14-19.55.27.334896 Resp - Enter an FTP subcommand.                                     
2013-01-14-19.55.27.334933 Resp - > NOOP                                                       
2013-01-14-19.55.27.334964 Resp - 200 NOOP command successful.                                 
2013-01-14-19.55.27.334996 Resp - Enter an FTP subcommand.                                     
2013-01-14-19.55.27.335028 Resp - > CD 'WMUploads'                                              
2013-01-14-19.55.27.335058 Resp - 250 CWD command successful.                                  
2013-01-14-19.55.27.335090 Resp - Enter an FTP subcommand.                                     
2013-01-14-19.55.27.335121 Resp - > NOOP                                                        
2013-01-14-19.55.27.335152 Resp - 200 NOOP command successful.                                 
2013-01-14-19.55.27.335184 Resp - Enter an FTP subcommand.                                     
2013-01-14-19.55.27.557637 PErr - CD error : Windows_NT                                        
2013-01-14-19.55.27.557732 Cmd  - QUIT                                     

Are you using SmartFTP?

My mistake. I thought this was a forum for any FTP errors.