OK... this may be a clue. Not sure.
For pages that won't load (where I get a grey screen and a 'view source' that shows only an empty body tag) but NOT for other pages, the error log shows a 'filter' message:
Jul 09 17:07:01 filtering
http://www.apple.com/downloads/macosx/ for document
http://www.apple.com/downloads/macosx/
Jul 09 17:07:22 filtering
http://www.apple.com/downloads/macosx/ for document
http://www.apple.com/downloads/macosx/
Jul 09 17:08:24 filtering
http://c.moreover.com/click/here.pl?r576416533 for document
http://c.moreover.com/click/here.pl?r576416533
I'm not sure what this means. What 'filter'? I have NO website preferences set and the overall preference settings I have are 'factory standard'.
I checked the plug-ins loaded. Nothing unusual. Cleared all input-managers (other than OW's crash reporting).
Still digging.