Hello,
The answer to this is to ensure that Gallery was installed correctly. I believe that the errors arise because if anyone tries to install the WordPress WGP2 plug-in without first installing the Gallery, then obviously it will be screwed.
The problem with my installation was my web hosting install, that failed on file permissions. That corrected, and reinstalled, then everything is fine.
Hope this helps.
The answer by jeremyclark13 does not help.
I too need to know where the Gallery2 URL is, and if it was set up by the plugin. There is nothing like that, and neither is there a file named embed.php that I can discover anywhere on the WordPress blog.
IF one does not have a gallery yet, how is it to be installed? Does it necessitate having a folder with some images in it? Does it require an embed.php file? If so, where is the latter?