A rare issue, presumably a bug in Finder (already reported to Apple). I wonder whether anyone else has seen the symptoms.
Selected frames from a screen recording show a volume named tall at the Computer level in Finder.
Sometimes the icon is of a traditional volume (not ZEVO);
sometimes the icon is of a ZEVO volume;
sometimes the icon is of a folder.
The content of the volume is not shown. OS X 10.8.2 seems to get no further than Calculating Size.
Workaround: force quit Finder.