Is "photos" a category or tag? Where does it come from?
From what you've told me, your Req URIs should look like...
... unless someone clicks a category in which case the format would be...
... with "category" being the actual word used.
Or, wait. Your pages are pages, and not posts? Shouldn't make a difference, but I see this:
Permalinks to pages don't work
If you've tried to navigate to a newly created Page and encounter an error, you likely need to update your Permalink structure. Remember, each time you add a new static Page to WordPress, new rules must be generated and updated to .htaccess (WordPress 1.X) or to the internal rewrites array (WordPress 2.X).
So, is "photos" a sort of page with three posts in it?
Still don't know about the missing letters, but there's something funny going on.
The program tries to parse your Req URI using the permalink structure as a guide, but these entries don't seem to fit that structure, unless I'm missing something.