problems burning a movie to disc via iDVD and Burn

I have been trying to burn a movie, (it's an .avi file), to be watchable on a DVD player. I tried using iDVD, utilising the "OneStep DVD from Movie" option. I go through the steps, the "encoding disc" dialog window comes up and a few hours later, with a few minutes showing left on the progress bar the disc gets spit out and a new message window pops up saying my disc has been created. I attempt to watch it via DVD player but all that appears is a green screen, I put it into my DVD player and same thing.

I downloaded the free Mac app, Burn, but have been unable to even add video files. I select "video" button at the top of the app windows, click on the + symbol to add files, click on the file to add to Burn but the file never is added to the list, even tried doing drag & drop but again the file does not get added. It only shows up if I select the "Data" button which as far as I understand is not applicable to burning a video file...or am I wrong and should be selecting "data" instead of "video?"

I am running OS 10.4.1 on a Mac Book Pro with version 7 of iDVD.

Thanks for any assistance!