Thats was wierd. i wonder what was actually causing it in the first place?
At any count, Im glad its working well for you now. TBH, I liked that game quite a bit. Looking forward to more adventures. Hopefully they add or offer more content in the future.
As far as Halo2, (Im assuming you have but..)
Have you tried navigating to the setup exe on the disc, and install the game as Compatability Vista SP1, and run as Admin?
I do not have the game and have nothing to really offer in regards to getting it running other than that
Its helped me in the past however for some GFWL games, especially for Fallout 3. I have wierd issues at first launch unless I install this way.