Are you using the same disk as yesterday? The only time I have aver seen this error (not with civ, but with some other games) is when I tried to make a copy of a disk and play of that. I used to do this all the time... Make a copy of the original as soon as I get it, and then play of it, so that I can leave the original in a safe place. Unfortuntaly, presumably because of piracy, many games companies have, in the last 2 or 3 years, made their disk un-copyable.
If it is the same disk, then I would have to assume that either the disk, or the drive itself, has somehow become damaged. The first thing I would do is try the disk in another drive to see if that works.
