I was testing how ZenPage works, and enabled comments on of the pages. This is the error message I'm getting:

The Zenphoto object you are requesting cannot be found.
Theme page: news=>This-is-a-test-ZenPage

The page exists and it's published. What can it be?

When exactly does that happen?

When I added a comment to a test Page in ZenPage default and hit the Add Comment button. The next page is an error page. What interesting the comments are actually added to the page, a notifications are sent via email, it's just a confirmation page that shows an error.

I will take a look if I can reproduce it.

I sadly cannot reproduce that, it works fine on my local install. (note that I am not able to test spamfilters liker Akismet or Spamassassin). Please try the zenphoto nightly and the zenpage svn version (you need to install both!) if that issue is still there.