Well, for those people who can’t/don’t want to update to the new version of BP, here’s the fix.
Make sure if you have a custom edit profile or registration template that you put brackets at the end of any multiselectbox field name that you’re using.
Then, you need to edit lines 400-421 of the BuddyPress core file: /buddypress/bp-xprofile/bp-xprofile-templatetags.php. It starts with case 'selectbox': case 'multiselectbox': and ends with break;
Note: this isn’t a very upgrade friendly way to deal with it, but if you’re stuck with BuddyPress 1.1.3 because of some custom written components, it’s the way to make it work.