Symphony.

Getting back into this Symphony thing and hit this one from my new host:

Your account is on a suphp server, which means that files/folders with 777 permissions will cause an internal server error.

A lovely 500 internal server error ensues.

This is despite my first vanilla test-run installation (with a bit of help from a support guy) was running fine.

I guess I made the dumb mistake of wanting to re-install from an ensemble of my dev version instead of jiggering what was running fine already.

Apparently, it wasn't permissions but ownership that was causing the problems. Duh!