Hmm, the plot thickens. The preview on the icons is linked to quicklook. Since we have preview of other files, you have a problem with SU’s quicklook plugin indeed.
, there seems to be some answers in this thread.
basically, it could come from a faulty install of the plugin into mac os, or the fact that you still have an older version (so it’ll try to start the old version with the new SU files)
You have a few solutions, one in the terminal, one in the SU app package (right-click on it, then show content)…