Hi! Sorry for the confusing error messages. I have seen this once or
twice during testing. I'll do my best to fix it in the next release.
The error messages, as you discovered, are spurious. The messages are
being sent just fine -- the plugin is a bit confused is all ;)
The FAQ (though very out of date) is here:
http://notoptimal.net/iphoto2gmail/faq.html
Thanks for the error report.
JI