I'm building a site with statamic (locally, right now) and I ran into this problem while trying to access the editor page for a page I created. I get the error message above when I try to open certain pages in the cp edit area. When I go directly to the pages' URL's, everything looks fine, and the edit pages were working fine until recently. I believe the only change I made recently was nesting these specific pages under another page. All other pages (i.e., the pages from other templates that aren't nested in this location) work fine in the editor. Again, the pages themselves look fine in the front end.
Here is the full error I get (I'm not sure what it means):