Well folks, while it appears that the patches have fixed World Series Baseball 2K3, it seems that you must disable IGR for it as well.
This is untested (because my Xbox is tied up right now with a game that has no in-level saves), but here is my experience:
Before I patched World Series Baseball 2K3, as soon as the game started it rebooted. After I patched it, I get the first screen (generic mlb screen), which it freezes at and has some annoying sound in a continuous loop. I also downloaded a zip file with the patched xbe's, just in case I hadn't done it right or missed some files, but got the same results.
I'm using an Xecutor 1, with EvolutionX 1.82XXX and IGR enabled in it.
I'll try disabling IGR later and see how that works.
But, does that sound like an IGR problem to you guys or just some corrupt file?