Same component scores, different overall score: what gives?

Your score remains the same. A 710 will NEVER go down to a 700. A Q47 might go from being 81st p.c. to 77th p.c., but you will still have a 710. Of course, a 710 might have been 93rd p.c. or something at a point in time, and might only be 91st p.c. now.

Matterhorn, that's a question that gets raised pretty often. No one quite knows how GMAC's scoring algorithm for the GMAT really works, so it's all speculative. But rjacobs is right in that you're compared to a pool comprising of all test takers within a specific time frame, and if a Q50 V41 is 99th p.c. when compared to that pool, then you get a 760, and if it's 97th p.c. then a 740 et cetera. The percentiles fluctuate all the time, albeit only slightly.