They posted twice on us by accident, but it was unrelated to the billing cycle. They updated as usual the day of our statement (the 18th) with a $0 balance, and then again about 10 days later with a balance. This was back when I only had a few cards, and I got dinged by TU for too many accounts with balances. (It was at Christmas time.)
I knew that it was an artificial score drop, and that it would come back, but I was curious, so I called Discover to politely ask WTH. They were baffled, and said they'd check into it, and about five days later (without my asking) updated AGAIN to show a back-to-$0 balance. (I had already paid it back down again.)
So I don't know what makes this sometimes happen, but if it's causing a problem, and you can't wait until the next normal date, you can call and ask them what's going on. They might restore it to the statement balance.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit? FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007