I have found that the method of installation affects the success of installation of new notification sounds. Using either direct connect via USB, or Wi-Fi File Explorer Pro, I can install MP3s into my SD/media/audio/notifications folder from my computer and get them to appear properly. DL'ing them directly from a site (most recently Oringz.com), onto phone, nor using Air Droid (which I like better the WiFI Explorer) doesn't seem to work properly. Hope it helps!
Excellent! This works, thanks.
is there a way to find out if it's an international model?