I've used LiveType since Apple made it available and have never seen the problem you describe. That doesn't mean it's not doing it, just that it's not "normal." I have experienced the problem you describe when working with the FCP scroll tools.
In either case, I'd start with trashing the appropriate prefs and repairing permissions. After that, any other "housekeeping" you feel will clean up the system. Maybe start a fresh project in LT as well.
The advantage to working in LT is that you have a live timeline and your output should match it one-for-one. If it simply won't, what I used to do is increase the duration of the scroll until I got all the content and export it (effectively pre-comping it) and then bring that clip back in and edit it to eliminate the "dead air." Crude but effective.