PHP - AJAX Image Gallery Management

I am getting a black box for images that I upload… is there a file format that is required (only jpegs maybe – all the images that are showing up with black boxes are png’s and gifs). Any thoughts on why this would happen? It is only the thumbnail that is not showing up correctly, everything else seems to be fine. http://superuntitled.com/photos/test.php?gallery=1

The error I get is:

Warning: imagecreatefromgif() [function.imagecreatefromgif]: ‘superuntitled.com/html/photos/uploads/Gallery 2/tumblr_krvgjwgsnX1qa9bmwo1_400.gif’ is not a valid GIF file in xxxx/xxx/superuntitled.com/html/photos/includes/functions.php on line 39

Hi, getting the same error message:

Installation There is a problem in the gallery folder. Please check your settings.php or the gallery folder.

Database connection: OK

There is a problem in the javascript folder. Please check your settings.php or the javascript folder.

There is a problem in the CSS folder. Please check your settings.php or the CSS folder.

There is a problem in the admin folder. Please check your settings.php or the admin folder.

There is a problem in the ajax calls folder. Please check your settings.php or the ajax calls folder.

There is a problem in the uploaded images folder. Please check your settings.php or the uploads folder.

There is a problem in the thumbnail images folder. Please check your settings.php or the thumbs folder.

There is a problem in the static images folder. Please check your settings.php or the images folder.

— I am currently working locally, on a MAMP server. Should there be any issues in doing so?