mac4t,
Please describe what exactly is wrong with the iDVD movie.
I have had problems with iMovie to iDVD recently that took me a while to resolve but I don't know if your problems are the same.
In my case the DVD produced by iDVD was interlaced and so I got horribly jumpy footage on my TV although it looked fine in preview in iDVD. My solution was to choose a non-obvious export setting in iMovie. I used Share/Export using Quicktime/Movie to Quicktime Movie and under options chose DV/DVPRO - NTSC, Current Frame rate, Medium Quality, Progressive, 16:9. I used no filters, and a size of 720x480 16:9, Letterbox. The resulting file imported into iDVD and produced non-interlaced (or at least non-jumpy

footage.
Unfortunately I now had a different problem. iDVD refused to see these new files as 16:9. The template menus showed the correct ratio but when I selected and ran the actual movie it was squeezed into 4:3 format. This seems to be an ancient problem in iDVD (why Apple never fixed it is anyone's guess) and I resolved it finally by passing the exported DV/DVPRO files from iMovie through
Anamorphicizer (also free) before reading into iDVD.
FINALLY I got a good DVD of my friends wedding from my HD source. I hope this helps you.
One more tip. Don't burn in iDVD, tell it to export an IMG file. It's faster than burning a damn coaster and you can mount the IMG and look at it in DVD Player to see if it's worth burning. I like the application
Burn for making DVD's. I've even used it to make a DVD that my PS3 will play as HD... another story.
Tim