Shopp 1.2.5 was released today.
It addresses an issue with PHP5.2 where after an upgrade you may find yourself locked out of your WordPress admin.
This does not occur with PHP5.3. If you can make the switch from PHP5.2 to PHP5.3, please do so.
You can upgrade automatically via the WordPress Plugins area.
Here is a guide for completing a manual upgrade in Shopp.
Same as before, please backup your WordPress before making any changes. You can easily backup WordPress with a tool like Backup Buddy.
If you run into any issues while upgrading, be sure to open a ticket on the Shopp Help Desk under ‘something broke’ so a team member can help you: https://shopplugin.net/support