I found a post on another forum similar to yours and he solved it by changing the cIOS with base 57.I am using the latest version of Usb Loader GX and the pal version of the Disney G-Force game. Every time I start a new game or try to load a saved game the loading screen stays in an infinite loading message not giving way to the game itself. This happens regardless of the cios used, even using the original game disc from Usb Loader GX also happens the same. It is the only game with which it happens, of course from the normal disk channel everything works as it should, so it is a Usb Loader thing.
However, if we restart the game once we have loaded it with Usb Loader, before starting or continuing a game, the game then works without problems. So if anyone has problems with this game because of the loading screen that never ends, just remember to restart the game (you don't even have to wait for all the screens to load before the main menu, just restart it as soon as you put it on).