On my laptop, running 10.10, whenever I plug in a thumb drive Nautilus will add an icon on the desktop and open a file manager window with the drive contents. This does not work for my 250Mb external hard drive: the icon is added on the desktop, but no file manager window pops up. Double clicking on the icon just causes some disk activity (on the system drive) and nothing else. Double clicking another time on the icon the file manager eventually opens. At first I thought this was related to nautilus-elementary, but after removing nothing has changed. How do I even start debugging this?
Update: suggestions below got me curious, so I "Safely removed" the drive, unplugged it and plugged it in again. This time it would open on the first double click (no automagic file manager window yet, anyway). Doing a quick "mount" in a terminal shows my USB drive is mounted as a fuseblock device. I suspect the first ineffective double click could be used to load/start the whole user space filesystem thingie.
Update: from what I can see after a fresh boot the hard disk is mounted as soon as the icon appears on the desktop, the only thing that doesn't work is double-clicking the first time. Right-clicking the drive and chosing "Open" always works the first time, seems like "Open" is not the default double-click action for external drives...
Update: Looks like there are a couple of bugs that could be related: