Well, the first thing I'd do is try doing exactly what Brucewrs did... call AquaTraders and try to see if you can get the right ballast. Worth a shot.
Second, you could consider upgrading. I build all my own lighting myself, so I really can't recommend one brand over another.
Third, you can do what we've been talking about... replace the entire unit. Here's Coralife's web site contact info:
http://www.esuweb.com/contact.asp
I'd call them first, and find out whether or not what we're talking about doing will work... run your two 96w straight pin PCs. Maybe they can even point you to an owners manual, technical drawing, or even better, a schematic so we can be sure.
You might seriously consider option 2 here. Lighting is expensive, but the Odyssea stuff is pretty low quality. It might be "telling you" it's time to move on up. The lighting system you have will make a great backup system if the halides are still functional....