Hi!
This might be a yet unknown but. I checked the function reference, and there was a change that I was not aware of, affecting this section only. I will make sure to resolve it in the upcoming release. If you want to resolve it manually now, you can do that by changing one of the plugin files:
(before you start, make sure to have a back-up, just in case)
1. Open up the wp-content/plugins/ajax-search-pro/backend/tabs/priorities/priorities_individual.php file on your server
2. Change it’s contents to this
3. Save the file.
Now, going to the priorities menu, and making changes should work again. Let me know if you need a help with this.