I took the WAIS-III and did extremely well on all the verbal subtests with one exception: arithmetic. But bad arithmetic skills didn't cause my low score; poor concentration did. I was in another world when I took the arithmetic subtest.
I took the WAIS-III to qualify for Mensa and scored two points away from the cutoff. If I get the arithmetic subtest readministered (the test admin. is considering), will my score be as valid, or will the "test-retest" effect inflate my score and make it a worse measure of my real abilities?
I believe there is a time limit for retakes; you probably have to wait six months for a retake to be considered acceptable.
Mensa now accepts a number of different tests so the easiest thing to do is to take a different test, or to submit your SAT or GRE scores.
Do you care about getting into MENSA (in which case, bone up on listening skills and take it again), or a "valid measure of your abilities" (which, actually, will have changed if you practice so both could still be valid... one of the things the Arithmetic test measures *is* concentration - it definitely isn't really measuring arithmetic abilities... the questions never get harder, just longer)?
IF you're that smart, then you should recognize that no test measures "true abilities." They're a snapshot of how you perform in a very specific situation, on certain pretty arbitrarily engineered tasks.