Custom File field with Event doesn't seem to work

I've added a custom file field to an existing civicrm data group used for events. All of the fields display on the Add event page, and all of the other fields (except for the new file field) work — when you put data in them, the data is saved. However, with the new file field, data is not saved.

I've confirmed that my file upload directory is correct, only because there are files from previous imports there, but no files from custom fields with attachments.

I found a related forum posting http://forum.civicrm.org/index.php?topic=6199.0, but that involved Drupal profile fields, and thus is going through Drupal's hooks. The issue I'm having is with Events, and it appears to me, is not going through Drupal's hooks, which is why I've created this new issue. Please advise. Thanks!