IDVD 4.0.1 quits when burning using Tiger

Question

I have been using iDVD for years and it has worked perfectly for all of that time. I recently upgraded to the new Tiger OS and since then I have been having problems.
I have a flat panel iMac with a 800 MHz G4 processor & 758 MB of RAM.
Every time I try to burn a disc it quits. Since it takes so long to encode I usually start burning before I go to bed and (expectedly) every morning when I check on it there is a message saying that "iDVD has unexpectedly quit". The dvds work when I play them, but for some reason I am unable to make copies. This is very inconvenient because I make wedding videos and usually need to make several copies and I can't afford to take 8-12 hours for every copy I need.
There seems to be a problem of compatibility between iDVD 4.0.1 and OS X 10.4.2
I see that other people have been having this same problem. Is Apple doing anything to fix it?

Answer 1

Just thought I should post back and let you know that I seem to be up and running again! Many thanks for all your help. I read through everything, and tried several of the suggested fixes.
First of all, I rebuilt the movie part of the project by importing the movie from the finder, rather than through iMovie. I tried a burn, but still nothing doing.
I then cleaned up a bit, as I did not have the apparently neccessary 20Gb of space- I had 17, so I deleted older files until I had 20.5Gb.
I then trashed the iDVD prefs, ran MacJanitor, Repaired Permissions, and restarted the computer.
Then, first try, my disc burned in a little over 15 minutes! Expecting the worst, I watched the whole thing on my DVD player (a 5 minute movie, and 4 slidehows with music and transitions), and it worked perfectly. I immmediately tried a second burn, and again it worked no problem.
Am I just lucky?
Again, thanks for all the advice posted here!