but I know now from your description that it did not happem in my past games. I will, however, be on the lookout when I get there. I just finished the Temple of Chaos and am in the Forbidden Vaukt right now so I have a ways to go before I get to Part 2.I have finished games in Part 2 as high as Level 311 (the trainer in Part 2 will go as high as level 511 if you have the patience), and I know that level 311 is much more than 16,777,216 XP (IIRC it was more than 35,000,000).
Why this is happening in your game and not in mine is a mystery to me although it sounds like it might be a combination of software (operating system) and hardware issues. I'm just guessing here as I am a long way from being an expert in any of those areas.
Hope you get that one figured out, it definitly should not be happening.