zeebe, i posted a reply to your topic in the OS X forum
here.
your problem sounded a bit strange, so i tried it myself...and you're right. you can only add the latest trailer, with the other 3, you get a 'iDVD does not allow..." error. i think there's some sort of protection or something when the trailer was encoded.
but parkds suggestion of exporting it in QTPro actually works. if you export it, the exported movie will be able to be added to iDVD. okay, now the big problem is what parkds mentioned: the trailers are letterboxed, so they end up getting squished to fill the 4:3 screen. i'm sure you'll be able to fix it in FCP, but i'll have play around in QTPro to see if it's do-able.
tr