Hi popcornninja,
Based on your other CAT/mock Scores - and the fact that you took this most recent CAT at NIGHT - it's likely that you were just too tired to perform at your best. You should want to take your practice CATs at a day and time that you are at your best mentally, physically and psychologically; for most GMATers, taking a test at the end of the day is NOT the best time for any of those states. If you've taken all of your CATs in the evening, then you might just have had a 'bad day' on this one CAT - but you should also consider shifting your schedule to take your CATs earlier in the day.
Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How long have you studied? How many hours do you typically study each week?
2) What study materials have you used so far?
3) On what dates did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
4) What is your overall goal score?
5) When are you planning to take the GMAT?
6) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich