Neil:
I'm not sure if this is Scintilla problem or not as I can't test Scite on OSX, but I opened this ticket for wxwidgets and would appreciate if you could take a quick look to confirm that it's not Scintilla. I have all the details (including the stack trace and the file it crashes on) in the ticket:
http://trac.wxwidgets.org/ticket/15621.
The short summary: when I load a file that includes some multi-byte characters, for example, \240\157\128\128, it crashes during painting of that character. wxSTC is using v3.2.1, but I didn't see any changes related to that issue in the Scintilla history after that version. Please let me know if you need any addtional information. Thank you.
Paul.