I just upgraded to the newest version of the guestbook... it was an issue before i upgraded and after. It didn't used to have this problem, maybe 8 months ago or so. The template page used to be fine. If it's PHP version related, then that could likely be the issue. I'm hosted by Lunarpages.
I've also noticed that the same type of error occurs in the admin page when it tries to list all of the databases on the "change password" page.