xautoload not loading class
Several things to consider.

*.php only looks in the folder itself. **/*.php also looks in subdirectories recursively. This seems ok in this case, but I want to mention it for other visitors.



The files[] = .. always requires clearing the cache.
If you have problems with this, drush rr (Registry Rebuild) is useful.



The core class registry with files[] = .. does not work for classes in namespaces.
xautoload does not change this.

The Registry Autoload module makes namespaced classes work with the core registry. But I don't know how well it works with the *.php-style wildcards.

Or, you can use hook_xautoload() to register additional namespace directories.