I have only fluxbox, not DE. Ubuntu 10.10
Still this is a problem Chromium 10.0.608.0 (68926) uses xdg-open and enters into a stupor at the "Open" the saved file, or "Always open files of this type" !!! Vicious cycle of downloads: browser -> xdg, xdg-> browser and so again 50-60 download!!! a distribution for people, what place? 
I have the same problem with chromium and transmission-gtk, to add torrent to my transmission-gtk. Browser itself opens a file with xdg...

 ~$ chromium-browser
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-event-sounds' of type `gboolean' from rc file value "((GString*) 0x7f8ba5484900)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-input-feedback-sounds' of type `gboolean' from rc file value "((GString*) 0x7f8ba5484760)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-button-images' of type `gboolean' from rc file value "((GString*) 0x7f8ba54846e0)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-menu-images' of type `gboolean' from rc file value "((GString*) 0x7f8ba5484860)" of type `gboolean'
[4653:4667:23525915482:ERROR:chrome/browser/extensions/extension_protocols.cc(135)] Denying load of chrome-extension://hcamnijgggppihioleoenjmlnakejdph/sounds/boing.mp3 from about:blank because the extension does not have access to the requesting page.
[4653:4667:23525988469:ERROR:chrome/browser/extensions/extension_protocols.cc(135)] Denying load of chrome-extension://gffjhibehnempbkeheiccaincokdjbfe/notify.mp3 from about:blank because the extension does not have access to the requesting page.
[4653:4667:23526167546:ERROR:chrome/browser/extensions/extension_protocols.cc(135)] Denying load of chrome-extension://hcamnijgggppihioleoenjmlnakejdph/sounds/boing.mp3 from about:blank because the extension does not have access to the requesting page.
sh: transmission: not found
Warning: program returned non-zero exit code #127
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-event-sounds' of type `gboolean' from rc file value "((GString*) 0x7febbc8ad900)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-input-feedback-sounds' of type `gboolean' from rc file value "((GString*) 0x7febbc8ad760)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-button-images' of type `gboolean' from rc file value "((GString*) 0x7febbc8ad6e0)" of type `gboolean'
In the current browser session creates a new window.
sh: transmission: not found
Warning: program returned non-zero exit code #127
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-event-sounds' of type `gboolean' from rc file value "((GString*) 0x7f99ce115900)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-input-feedback-sounds' of type `gboolean' from rc file value "((GString*) 0x7f99ce115760)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-button-images' of type `gboolean' from rc file value "((GString*) 0x7f99ce1156e0)" of type `gboolean'
In the current browser session creates a new window.
sh: transmission: not found
Warning: program returned non-zero exit code #127
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-event-sounds' of type `gboolean' from rc file value "((GString*) 0x7f7c0283c900)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-input-feedback-sounds' of type `gboolean' from rc file value "((GString*) 0x7f7c0283c760)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-button-images' of type `gboolean' from rc file value "((GString*) 0x7f7c0283c6e0)" of type `gboolean'
In the current browser session creates a new window.
sh: transmission: not found
Warning: program returned non-zero exit code #127
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-event-sounds' of type `gboolean' from rc file value "((GString*) 0x7ff6a5a52900)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-input-feedback-sounds' of type `gboolean' from rc file value "((GString*) 0x7ff6a5a52760)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-button-images' of type `gboolean' from rc file value "((GString*) 0x7ff6a5a526e0)" of type `gboolean'
In the current browser session creates a new window.
....
....

~$: xdg-open TTT16250.torrent 
sh: transmission: not found
Warning: program returned non-zero exit code #127
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-event-sounds' of type `gboolean' from rc file value "((GString*) 0x7f71fbdf4900)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-enable-input-feedback-sounds' of type `gboolean' from rc file value "((GString*) 0x7f71fbdf4760)" of type `gboolean'
Gtk-Message: (for origin information, set GTK_DEBUG): failed to retrieve property `gtk-button-images' of type `gboolean' from rc file value "((GString*) 0x7f71fbdf46e0)" of type `gboolean'
In the current browser session creates a new window.