As the subject says, it appears that qBittorrent (3.1.8 at the moment) doesn't appear to know how to properly handle network directories.
The RSS downloader dialog accepts a network directory in the rule definition just fine, but when the transfer is completed, an I/O error occurs.
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Eg. if I've got my save directory defined to "\\NAS\Video\TV", a following I/O error is recorded in the execution log:
14/03/2014 07:59:44 - Reason: Greys.Anatomy.S10E15.HDTV.x264-LOL.mp4 file (C:\Program Files (x86)\qBittorrent\//NAS/Video/TV/Grey's Anatomy\Greys.Anatomy.S10E15.HDTV.x264-LOL.mp4) error: The filename, directory name, or volume label syntax is incorrect
14/03/2014 07:59:44 - An I/O error occurred, 'Greys.Anatomy.S10E15.HDTV.x264-LOL.mp4' paused.
I'm pretty sure the qBittorrent binary directory shouldn't be prefixed into the path.
The directory is obtained from the destination directory dialog as above, ie. with backslashes, but somewhere along the line they get converted to normal slashes. I'm guessing this wouldn't be a problem though.
[/suspicious]