Comment 3 for bug 251991

I can also confirm that issue.

It's happening with a External USB Hard Disk.

And also this:

My second internal hard drive appears on gnome places but nothing happens when I click on it.

No error message, nothing.

Nautilus apparently doesn't know how to mount my slave hard disk.

The odd Thing. It works on the Live CD. Behaving just like described above.

I can mount manually.

Hope that helps.