LOL you are right...
Which version did you initially install? 2.4?
With 2.5 BIGACE sets permissions as mentioned in the install.php file:
define('DIRECTORY_PERMISSION', 0755);
define('FILE_PERMISSION', 0644);
The easiest way to change that is a little php script, which changes permissions recursive, it must be somewhere here in the forum

The owner indeed shouldn't be changed anymore with 2.5. Is your hoster using SafeMode or any other nasty PHP hardener that tries to "fix" permission?
If you cant find that script, I can have a look later on, busy right now ....
