I have to agree my score dropped from 559 to 532 and the only change I had was a mortgage broker checking my credit (just 1 time) and paying off an old collection acount and I freaked out in tears. Because I am trying to refinance and cashout but its very stressful trying to increase your scores by paying off old accounts.
You know what you may never know what caused the score increase, but I hope ot will help you to lock in an even better rate, good luck on your mortgage shopping.