Membership: Step 1 generating a blank page/not loading after submitting account creation

Using WP 3.3.1 + Membership Premium 3.0

- Username does not previously exist in DB
- User loads 'register page' (Step 1)
- Step 1: User fills-in form. Hits submit, page reloads, is completely blank (header, H1 title, nothing else, no error message).
- User was successfully created in WP backend (inactive, no membership/subscription).

Activated/deactivated various plugins.Emptied cache. Completely stumped.

Help!