Have you been an upstanding card-carrying citizen? Watch out. Even one small gaffe can send your credit card interest rate through the roof.

As many as 39% of credit card issuers now use what is called the "universal default" clause to raise interest rates on customers who pay their bills late, according to a recent Bankrate.com story. The dirty little secret is that the clause enables lenders to raise interest rates based not on your history with them, but based on your payment history or credit activity with other companies.

Fair? Maybe not. But it is completely lawful for them to do so at any time.

Your cardmember agreement (you know, that leaflet written in microscopic type in the acceptance envelope with all the deals for rental cars, hotels, and "Kittens in a Basket" porcelain figurines?) spelled out the lender's freedom to raise your interest rate at any time. When you signed the card and activated the account, you agreed to these terms, like it or not. Pretty much every lender has that clause built into the contract.

That said, customers who get hit with a higher interest rate have several avenues of recourse:

1. Pay off your balance as quickly as possible and then resolve to pay your balance in full every month from now on. That way, the interest rate doesn't matter.

2. Roll your balance over to a new, lower-rate credit card if you are not able to pay it off soon. (See if The Motley Fool Visa is competitive with other offers.) However, you might want to keep your old line of credit open, especially if it is one of your older accounts. Older accounts help establish a long credit history. Plus, having just one credit card with a high balance can lower your credit score. Just make sure to pay the balance off ASAP after you've rolled it over.

3. Look at your credit record under the same harsh lens the lending industry uses. It's best to see what is on all three of your major credit reports so you can resolve any boo-boos. Our partner True Credit offers a 3-in-1 credit report and credit score for $29, which is one of the best offers I've seen.

4. Wait it out. Most dings on your credit report will disappear after seven years. The good news is that it doesn't take that long for lenders to consider it old news. Your recent good credit behavior weighs much more heavily in your favor than one blip a few years ago.