Lg Gw620

My LG GW620 rang this afternoon and instead of the ringtone I'd selected from the music library it played one of the standard ringtones. Confused I entered the music library to find all of the ringtones I'd downloaded from www.cellsea.com (about 20) gone save for about 4.

The only thing I've done today differently is turn the phone off and on again because the screen froze but that's happened before with no problems.

Any ideas?

Thanks.