To ‘default’ the listings to Alphabetical would be a modification of the core, however, simply adding the following to your while (bp_has_component()) statement should get them in alphabetical:
A Blank page typically means an error is happening in PHP, however if your hosting provider or php.ini configuration is set to NOT display errors, you will see a blank page.
See if you have a way to set your display_errors on in PHP.ini or if you have access to the code you can try temporarily adding the following to your wp-config.php:
This may give you the ability to see the error you are getting and troubleshoot from there. Just be sure to remove these two lines from your wp-config.php once you get the errors as it will show all errors and warnings to visitors while in place.