just yesterday i install xfce on my ubuntu machine to change from gnome. while logged into an xfce session i tried running transmission and it started fine until about 5 minutes later it just disappeared. i tried using the restore hidden windows tab with no luck. i tried launching it again from the menu and received same results. last i tried from the terminal and received an error "Xlib: extension "RANDR" missing on display ":0.0".

i did have my external hdd connected and running at the time but from what appeared it unmounted sucessfully. any ideas on how to fix this?