This error occurs when the requested file contains one or more Unicode characters in its file name. For security reasons, certain characters are disallowed in file names. When Unicode characters are used, they are converted to the closest ANSI equivalent that is available in the code page of the server operating system. Unicode characters that do not have exact ANSI equivalents might be replaced with a disallowed ANSI character. To prevent a disallowed character from appearing in the file name, it is converted to a caret (^).

To avoid this issue, do not use Unicode characters in file names that are used on an FTP site. If Unicode characters must be permitted, only use those that have a direct equivalent (one-to-one mapping) to the server code page.