location of downloaded files

1- from Firefox, I choose a torrent file and open it with transmission
2- in the pop-up window, I choose the location : Other then navigate to the desired directory (on a external disk)
3- download begions
4- Choose the "Open Folder" option : the download is in the default download folder.

BUT when I choose "choose location" I can move it in the right place, and continue the download where I intended it to be

Apparently, the first dialog is not taken in account....
May be this is caused by the use of an external USB disk?

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: transmission-gtk 2.82-1.1ubuntu3
ProcVersionSignature: Ubuntu 3.13.0-29.53-generic 3.13.11.2
Uname: Linux 3.13.0-29-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CurrentDesktop: Unity
Date: Mon Jun 9 15:44:16 2014
InstallationDate: Installed on 2014-05-24 (15 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
SourcePackage: transmission
UpgradeStatus: No upgrade log present (probably fresh install)