Hi bitanrc,
First off, a 630/Q49 is a good score (it's right around the 75th percentile overall), so it could be enough to get you into your first-choice School. As such, a retest might not be necessary.
GMAC has publicly stated that the Official Score that you earn on Test Day is within +/- 30 points of actual ability. Assuming a similar 'swing' in how your CATs function, your score results all revolve around a 650 (with your Official GMAT Score at the lower end of the range).
Since you scored higher on almost all of your CATs, I have a few questions about how you took those Exams:
1) Did you take the ENTIRE CAT each time (including the Essay and IR sections)?
2) Did you take them at home?
3) Did you take them at the same time of day as your Official GMAT?
4) Did you ever do ANYTHING during your CATs that you couldn't do on Test Day (pause the CAT, skip sections, take longer breaks, etc.)?
5) Did you ever take a CAT more than once? Had you seen any of the questions BEFORE?
GMAT assassins aren't born, they're made,
Rich