THE INFORMATION IN THIS ARTICLE APPLIES TO:
File upload fails if a double percent sign %% is in the name.
Remove the percent signs from the file name or use the Web Transfer Client (WTC) for uploads instead of the Plain-Text Client (PTC).
The PTC uses a form-based upload in a browser which, for security reasons, won't allow the file name to be modified after the user has selected it via the file browser dialog. The server expects file names to be URI encoded; to encode the file name so that a double percent sign %% makes it to the server, the client would have to modify the file, which isn't allowed. Therefore, if a file name contains %%, upload of that file to the server will fail. (Downloads of files named with %% work, because EFT Server can modify the name.)