Why can't iMovie properly render titles?

I use iMovie 6 occasionally for small film projects (because the new iMovies are bogus) but occasionally my titles turn to sh*t. In the preview they look wonderful, but when it renders iMovie compresses the crap out of them, even when it’s over black.
I have scoured forms and other sites and can’t find anything that works. Has anyone had a similar experience or know of an answer?