Weirdness with a dmg: Try to mount it, but it does not appear in the finder. So I drag it to the trash and try downloading it again. This time it works fine, so I do what I need, eject it, and drag the second copy to the trash. Try emptying the trash... fails because one of the dmgs is in use. I check finder, but nothing appears as a mounted volume. Drag the undeleted copy back out of the trash. Open Terminal.app, and see that it is mounted. So I unmount it in Terminal, and try dragging it back to the trash. I still cannot empty the trash because the dmg is still "in use", even though neither the Finder nor Terminal report it as mounted. How do I get rid of this thing?