Thanks martimiz -- that's interesting. Am I able to configure which version of Apache MAMP 3 is using (I'm not running MAMP 3 Pro)? I didn't see that as an option! I'm running Mavericks (not Mountain Lion) but obviously it's nothing to do with that.
Agree about starting with a completely fresh, out-of-the-box install of SS to see how things run. That was my plan -- when I have a moment to investigate further. It looks as if something got broke...