I just burned a video with iDVD 7.1.1. It was basically a slideshow I made in iMovie 6.0.3. that I converted it to qt (full quality). I burned it on my MacBook Pro (266 GHz) (OS X 10.6.8) with about 100 GB of free space. I did not using my computer while it was burning. There is occasional pixilation problems on some images which I have had before and attribute to the Ken Burns effect (even though it has been cancelled for the image) but the real problem is a pulsing of the background in all of the images. This shows up during playback on my computer although it is not too noticeable, but it is really bad on my plasma TV I've made many of these videos - some on the same computer with the same software before but have never had this problem. Any advice; I find myself very hesitant to hare the video with my fellow divers (who know I am a Mac user).
With iMovie 6 just close iMovie and drag the project file into the open iDVD window being careful to avoid any drop zones in the menu. That will avoid having both iMovie and iDVD encode the slideshow and only have iDVD do the encoding.