I've just tried to set up register Plus 3.5.1 after reading up and seeing that most people do get it to work with WP2.7.
Once I set my options and press save I get the following error
Fatal error: Out of memory (allocated 36175872) (tried to allocate 4197252 bytes) in /homepages/12/xxx123456789/htdocs/pnp/wp-includes/wp-db.php on line 447
I have changed my memory allocation in settings.php to 48 then to 96 and still get the error..
Any ideas?