Are you changing the bit rate of the snippets?
I haven't tried playing around with making my own ringtones yet, but I've read a lot about it on HoFo and it seems that bit rate is very important. It might take a few tries at different rates to find exactly what your phone wants.
Of course, there's lots to learn from HoFo, and I believe you're already on there, yes?

I, too, just got a new phone- Motorola Z6C on Verizon. Eventually I'll start playing with it, but for now I'm just getting it running and used to it.