ive never had the problems that youre having... first of all, are you sure it was shot in HDV mode? second, i wonder if maybe you have your camera set to downconvert to SD in camera on capture?
when i say "uncompressed" i mean, go under the file menu, pull down to new then over to new - sequence. once thats there select it and right click to pull up settings. there you can set it up to be 8bit uncompressed. then drop your earlier sequence into that one - then export a reference movie.
there may be a newer or better way, from from my tests and others workflows that ive read - this seems the best approach...
i havent used idvd in quite some time, so i cant promise. but i dont know why it wouldnt accept a reference movie just as dvdspro does...?