Hi rafgimenes,
First off, a 660 is a strong score (it's right around the 80th percentile), so you might have enough of a score right now to get you into Business School.
GMAC has publicly stated that your Official Score on Test Day is within +-30 points of actual ability. Assuming a similar "swing" in those practice CATs, your Official Score is 'in range' of your practice scores (albeit at the low end).
There's also the possibility that something you did during your practice was unrealistic (re: non test-like) and that difference (or differences) could have impacted your performance when you faced the Official GMAT. To that end, here are some things to consider:
1) What were the Quant and Verbal Scaled Scores on your Official GMAT and on each of your CATs?
2) Did you take the ENTIRE CAT each time (including the Essay and IR sections)?
3) Did you take the CATs at the same time of day as your Official GMAT?
4) Did you take them under 'test-like' conditions?
5) Did you do ANYTHING that didn't 'match up' with Test Day (re: skipping sections, pausing the CAT, taking it at your home, listening to music, etc.)?
The sickness that you described could have easily impacted your performance (even if you didn't realize it) and there could have been any number of other "physical" issues that effected your performance on Test Day. The likeliest explanation is that you just made a few little mistakes - regardless of the cause, that's always what costs Test Takers points.
GMAT assassins aren't born, they're made,
Rich