I had the same problem, so I changed the names of the get_categories to _get_Galcategories, but now I have something strange:
Fatal error: Call to undefined function get_Galcategories() in /public_html/galeria/index.php on line 80
i think that it is declared...
I cleared cache, and now I get:
Fatal error: Cannot redeclare get_categories() in /public_html/wp/wp-includes/category.php on line 22
I checked the files, and there is no get_categories() in them - I mean 4images.
(I am trying to integrate the wordpress header and footer to the 4images template)...