The error implies that the file:
Connections/powergallery.php
wasn't uploaded or was deleted somehow. I'd need FTP access to fully debug.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.