No chance you saved the .image file iDVD created before burning the DVD? Or did you go straight from iDVD to DVD burn?
I do have the full project converted to iDVD and it plays on the computer
What format or file extension is the file that you are playing on the computer here? How are you playing this on the computer?
To bad, while it won't help in this case you might want to think about having iDVD make the .image file and then burn the DVD. This way if you need other copies you can just copy the .image file to DVD with going through the encoding again.
For now maybe if you post the encoding error you are getting someone might have an idea.