Unable to create discount set

Entered discount set to default Fall Fundraiser Dinner as indicated in attached image. When clicking Save, got the following error:

Fatal error: require_once() [function.require]: Failed opening required 'CRM/Order/DAO.php' (include_path='.:/Users/josephmurray/GoogleDrive/Sites/civiaccounts/sites/all/modules/civicrm:/Users/josephmurray/GoogleDrive/Sites/civiaccounts/sites/all/modules/civicrm/packages:.:/Applications/MAMP/bin/php/php5.3.14/lib/php') in /Users/josephmurray/GoogleDrive/Sites/civicrm/trunk.civiaccounts/CRM/Core/ClassLoader.php on line 99

One of the new popup messages appeared on next page load saying the save had been successful. Attempting to go back to the fees page caused error above to reappear.

Also, a warning appeared on the next page:
Warning: require_once(CRM/Order/DAO.php) [function.require-once]: failed to open stream: No such file or directory in CRM_Core_ClassLoader::loadClass() (line 99 of /Users/josephmurray/GoogleDrive/Sites/civicrm/trunk.civiaccounts/CRM/Core/ClassLoader.php).

Looking at the civicrm_price_field_value table when doing this a few times, it appears that the civicrm_price_set is created for all of the discount price sets, and a civicrm_price_field record for each one. However, the set of records in civicrm_price_field_value for each of the records in civicrm_price_field were incorrect: all but the last had a price_field_id that was one too large, and the whole last set were missing.