re: Paying off a credit card too soon?

My personal experience in a similar situation.. My credit score was sitting still at slightly above average for a couple of years. I got an AMEX rewards card that was 0% for a year, so I put everything on it and payed only the $35 monthly min. payment. My credit score increased dramatically throughout that year, and there were no other big account changes. Once the year passed and I paid the lump sum, my credit score started decreasing at about 2-3 points per month, again with no other account changes.

I don't really know how it works. All I know is that it's retarded.