Hi Fc733,
What you describe certainly sounds strange - and it's worth further investigation. That having been said, if the issue only occurred during the IR section, then that would have NO impact on your Overall Score out of 800 (since that's based on your Quant and Verbal Scores). If the issue occurred in the Verbal section - and we assume that the answer you submitted each time was being applied to a totally different question - then your drop in Verbal Scaled Score would likely be gigantic (the 'net effect' would be the equivalent of randomly guessing through the entire section). This is meant to say that the differences you noted between your CAT Scores and Official Score are probably NOT due to the issue that you're describing.
To properly assess this drop in score, 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?
2) What study materials have you used so far?
3) How have you scored on EACH of your CATs (including the Quant and Verbal Scaled Scores for EACH)?
4) What were your Quant and Verbal Scaled Scores on the Official GMAT? Is this the only time that you've taken the Official GMAT?
Goals:
5) What is your goal score?
6) When are you planning to apply to Business School?
7) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich