Well yea, thats based on the entries in the array inside index.php.
it doesn't convert to lower/uppercase so it looks for the key that matches exactly the key.
(Btw xfir: I think you can turn off/on case sensitivity thru a setting in php.ini, assuming you can edit php.ini, which isn't the case on this system.)
As far as for the filesystem, it's picky for filenames. (and unfortunately, the only way to change this is to modify the kernel and recompile, and only root can touch vmlinuz anyway).