FTP error I don't understand...

Hi All

I'm trying to do a physical file to physical file FTP from a V5R1 system to
another V5R1 system.  When I run FTP interactively, I see the following:

> ftpid                                                                        
  331 Enter password.                                                          
  230 FTPID logged on.                                                         
   OS/400 is the remote operating system. The TCP/IP version is "V5R1M0".      
  250  Now using naming format "0".                                            
  257 "QGPL" is current library.                                               
> bin                                                                          
  200 Representation type is binary IMAGE.                                     
> cd aplasmtst                                                                 
  250 "APLASMTST" is current library.                                          
> lcd mrpdlib                                                                  
  Local working dirctory is MRPDLIB                                           
> put pc210p pc210p                                                            
  200 PORT subcommand request successful.                                      
  426-Unable to open or create target file PC210P in library APLASMTST.        
  426 Data transfer ended.   

What is the "426 - Uanvel to open or create target file error"?  The user,
FTPID, has *ALL authority to the target file.  The target file is not in use. 
The from file is locked, but since the FTP is doing a PUT, would that matter? 
I've tried this under different user ID's, and different target libraries, and
the result is always the same.

Thanks!

-Ed