IDVD unexpectedly quits and/or video freezes during burn

Question

Please help! I'm going crazy trying to get a completed video project burned onto DVD. I have three video programs (one is a slide show), all created in Final Cut Pro and saved as either Final Cut Quicktimes or Quicktime movies using H264 compressor. The programs are imported into iDVD 4.0.1 (they cumulatively amount to less than one hour). Two different things are happening. Sometimes, iDVD churns for 16 hours, spits out the DVD, and says it unexpectedly quit. The DVD plays, but the slide show program freezes about 3/4 into (audio continues but video freezes). Other times, iDVD churns for hours and hours, only to quit and spit out a blank DVD.
This has never happened in the past. I've never before had trouble burning DVDs. The only change I recently made was this: I changed the name and password of the administrative account user. Also, this computer was iSync'd with another mac and about a week ago, all my preferences disappeared and programs opened as if for the first time (although nothing on the hard drive was lost).
Here's what I've tried: MacSweeper (although it has authenticaltion problems - I authenticate and then everytime I try to run it, it says it's not authenticated, so I can't tell if it's working), MacJanitor, I've checked all the preference settings and nothing comes up in error. I've also tried the Easter Egg approach and I got the same result (freeze 3/4 through).
Here's what I have: iMac G4, 800 MHz CPU, 1 GB memory, OS X (10.4.2), iDVD 4.0.1.
The slide show program is the only one messing up on the burned discs. Do you think it has anything to do with the new H264 compressor (in the past I've never used that, and the other two programs - which are fine on the DVD - are Final Cut Quicktimes).
Help me please - before I do something violent to this computer!!! Thanks for any advice.
Shannon

Answer 1

Thanks for your suggestions, David. My remaining issues are these, and anyone with ideas is welcome to chime in here:
First, I've never encountered this problem in the past, even with the same amount of available disc space. It seems like the Tiger upgrade is what's causing the problem, but so far it's been impossible to isolate. Has anyone heard anything about this or found a permanent solution?
On that same note, I understand what you're saying about an external drive. I don't have one, and it seems superfluous that I should need to spend money on one when this process worked fine a year ago. But I guess I'll try it if nothing else works better.
Second, fortunately, I wised up to the Disk Copy solution to make back-up copies of my ONE usable DVD. But I'm extremely concerned that I will encounter this same problem the next time I need to burn from iDVD. I have no idea why this one disc worked and all my other attempts failed. There must be something identifiable going on in all these similar cases, and it doesn't make sense to me that the permanent solution lies in somehow working AROUND iDVD instead of through it. And I guess I won't spend the money to upgrade to iLife '05 if the possibility exists that this problem will persist.
So there are my lingering concerns and frustrations. For now, I'm walking away from this project with exactly ONE useful DVD produced from iDVD out of approximately 20 attempts. Something's wrong with this picture. Ugh!