I got the "Sorry! Please insert your original Halo 2 game disc" error after Quarantine Zone and High Charity. It was a duplicatable error on those two levels specifically. Annoying, but ultimately harmless. You get the achievement and the next level is unlocked on the level select screen.

There's some button assignment glitches. With the Banshee, I had Secondary fire (FRG) set to right click and boost set to left shift. But when put into practice, right click did nothing at all. I had to switch Secondary to left shift and boost to right click to get both functions to work.

Also, I can't seem to get friendly AI out of vehicles. I have all the old X-button functionality mapped to MMB and it says "Hold Middle Mouse Button to enter vehicle", but the pilot or driver just stays in his seat no matter what.

MS's "thorough" QA is a joke. All it does is delay us getting fixes for the myriad of issues that they invariably miss in the first lengthy go-around.