So I was happily grabbing a screenshot with Skitch earlier and dragged it to the desktop as always to have it saved there as a .jpg file - and it kept doing nothing as I tried.
Eventually - after a very, very long delay - I got a Finder error message:
Ah, ok - but I never asked for any file to be invisible. WTF? Also, I can't find a Finder (or other) preference that says 'Please make **** invisible just to add a little spice to my day') so that I can toggle it back off. And to add to the fun, I cannot find the file in question via Finder, Spotlight, or Quicksilver.
Anyone ever come across this / have a fix? Via Google I can only find quite old (pre Leopard) article like
this one at Macrumors that mention the issue.