No issues with custom text ringtones here, and I've been using bite for that for nearly a year. I'd say check their forums first and see if the problem has been posted there, otherwise email their devs; contact info and instructions on how to reach them are on their site. They're very good about following up.
Also, two possible conflicts that I've heard of before are with LockInfo and ToneFXs. If you have either of those, it's worth seeing if they're the problem.