OF course my first thought, since you're using 4x media, is that you need the
SuperDrive firmware update, but I'm sure you already tried that.
After about two dozen burns I can honestly say that I've only had iDVD lock up on me twice. As a rule I totally ignore the 'time remaining' estimates (which are usually pretty innacurate) and have taken to running the CPU monitor in the background just to make sure it hasn't frozen.
But that is the
only thing I will run while burning, and I have a dual 1Ghz. For your 450 make sure you are not running
anything else when burning. I mean nothing. Make sure you don't have a screensaver or energy saver set, and disconnect from any network you might have.
Also, how much RAM do you have? And someone also told me something once about having enough free HD space...can't remember what, but if your HD is too full that might be a problem(?). Have you tried any other brands of DVDs?