AHA!, FiXED IT!
Basically, for anyone else in the future, struggling with this problem…
Check your Debug information from wordpress. Mine was complaining about two blank lines at the end of one of my php files (widgets.php)
deleting these fixed the issue.. Bizarre.
to enable debugging, open your wp-config.php and insert the following above the line
/* That’s all, stop editing! Happy blogging. */
insert this ABOVE that line
define(‘WP_DEBUG’, true);
@ini_set(‘log_errors’,’Off’);
@ini_set(‘display_errors’,’On’);
This will display the errors inline, (and will hopefully help you see the issue)
Good luck!