http://www.freedownloadmanager.org/board/viewtopic.php?f=1&;t=17803

This is a problem with FDM 5.x not converting slash character ( "/") in video title to underscore. There may be more characters in video titles that are not allowed in filenames under Windows, f.e.

< (less than)
> (greater than)
: (colon)
" (double quote)
/ (forward slash)
\ (backslash)
| (vertical bar or pipe)
? (question mark)
* (asterisk)