PEople if you are playing with a retail version of the game then and this if you are not using a no cd crack if there is one no clue dont care, but any how the game will run as fast and keep up as fast as your rom drive is, after hours of play i get those pasty problems like was described, i i just open then close the rom drive with the disk in of course and bam it stops the problem and i pick up where i left off at. So key here is i need a faster rom drive and most likely so do those having this same problem.
But just my experiences is all i am going on
The game only uses the CD to read at the game start. Everything is loaded of the hard drive, the CD is only used for installation and checking the game is legit. Plus in this day most DVD drives are maxed out and all the same speed so I very much doubt this is the case.
But then im using the Steam version, but it shouldn't be any different for the retail boxed version.