If you're reading this post than you probably had a blocked UCBench score. What we once considered "luck" turned out to be a design flaw of the benchmark, documented by a fellow member of the HWBOT community (credits pending) and personally tested for veracity.
TL;DR: The Passwords Checked column must be in ascending order (A<B<C etc)
How to make sure you're not going to get a bugged score:
Make sure that thread selected divided to total available threads (cpu threads) is not an odd number.
Let's take an example: -cpus=24,53,60 ; with a physical CPU that has 4 threads (4c/4t, 2c/4t).
Benchmark only cares about every other second thread (24,53,60 -- A,B,C,D,E,). This example will be bugged since 53 divided by 4 will result into an odd number (13) AND is also second in line. If we were to rearrange our original choice, we could return a valid result using: 24,60,53. Notice that since second number divided by 4 is now an even number, the result won't be affected.
We will refer to this rule as "A<B<C", in case you're wondering what mambo-jumbo were talking. Speaking of which, scores that resemble "A>B~C" are technically bugged but they will be at moderator's choice, with the chance of staying in the rankings.
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UPDATE 16 May 2014: TL;DR
UPDATE 22 June 2014: Typo in A<B<C