I've just tried it.
When Hide similar components is checked, it works fine.
When Hide rest of model is checked, it ignores the selected entity and zooms to the origin.
Must be a bug.
I guess we just need to select, then zoom, then hide.

K-tools does the same job
Use the Round Edge function.
I have it assigned to a shortcut key.
Works great!

Fixed it myself!!
Its late ... I forgot about the SmustardOrganizerExcludeFolders exclusion list.
Added the Subsmooth folder to the list and all is well with the world again

I have downloaded the Plugin and installed as directed.
However, I am getting this message when I start SU
Error Loading File organizer.rb
C:/Program Files (x86)/Google/Google SketchUp 6/Plugins/Subsmooth/subsmooth.rbs:1: no .<digit> floating literal anymore; put 0 before dot
RBS1.0 ^ C:/Program Files (x86)/Google/Google SketchUp 6/Plugins/Subsmooth/subsmooth.rbs:1: syntax error RBS1.0
^
Any ideas?