It sucks but there is nothing you can do about it. Credit card companies are preparing for the new laws next year (I think) that will prevent them from raising rates among other things, so they want to raise them now while they can.
The same thing happened to my mom, didn't have a late payment for over a decade, and then a couple months ago she was ONE day late. They doubled her rate.
I work for a credit card company. Some of the laws have already gone into effect, most of the remainder come in February.
The one that everyone is noticing is the new "opt out" option. The credit card company must advise you in writing of any pending interest rate changes, and you have the option to close the card and keep the same interest rate. You still have your balance and APR, but you lose the ability to charge.
The original poster is referring to the "Penalty APR" issue. Two late pays in 12mo rolling period = massive APR. If you are always paying balance in full, then set it up on Auto-pay or something.
Closing the card by the user is not really a big hit on the credit. The only things to worry about are that closing this card will not raise your limit/balance ratio, lower average age of accounts, and reduce diversity of credit line types.