Users report Halo 3: ODST disc read errors.

[AlkamistStar]

Garnett said:

The messed up thing is that its the opposite of whats happening to me,If i play off the disc its fine,if i play from the HDD it screws up.

 

And yes Firefight lags ,most of the time it is because of Vehicles.

Bungie has stated time and time again, not to install Halo 3, or ODST (since it's on the same engine) on the hard drive, maybe that's why your having problems. Run the game from the disc.