Report your bugs here - if someone else has already mentioned the same bug, just add on to their post with as much info as possible to make the hunting easier.
Your new computer is 64-bit and hence Bookpedia is running in 64-bit mode and can only load 64-bit plugins. Two options: Open the latest Xcode and rebuild a new version of the plugin that will include 64-bit support (does this automatically by rebuilding) and replace the plugin. Second option use "File -> Get Info" on Bookpedia and check the "Open in 32-bit mode" check box. When you relaunch Bookpedia it will launch in the older 32-bit mode that is currently still supported by the latest version and it will be able to load the 32-bit plugin.
Indeed iSight has two different code paths for 64-bit and 32-bit. It's likely the element that will force me to rewrite and make Bookpedia 64-bit only in the future.