I also have this problem on 10.10 amd 64 Usb drives are not seen when plugged in. if I run Dolphin as a user not Root or sudo the Usb drive is seen. If I mount it from Dolphin and then exit dolphin I can see it on the desktop and Nautilus also sees it. Nautilus will un-mount it but can not see it if replugged.
This problem has arisen in the last month.
Also related when I click on "places" " home" I get Dolphin but if I click "places" then " computer" I get Nautilus
I also have this problem on 10.10 amd 64 Usb drives are not seen when plugged in. if I run Dolphin as a user not Root or sudo the Usb drive is seen. If I mount it from Dolphin and then exit dolphin I can see it on the desktop and Nautilus also sees it. Nautilus will un-mount it but can not see it if replugged.
This problem has arisen in the last month.
Also related when I click on "places" " home" I get Dolphin but if I click "places" then " computer" I get Nautilus
Phil