I thought this paragraph might help you.
"What many people don?t know is that credit scores don?t distinguish between those who carry a balance on their cards and those who don?t. So charging less can also improve your score -- even if you pay off your credit cards each month."
From -
http://moneycentral.msn.com/content/...ing/P38052.asp
So it sounds like you should use your credit cards less and just carry a small balance. To the credit reporting agencies it might look like you're always carrying a large balance which really hurts your score.