I understand your frustration. Your debt to credit ratio can have a big impact on your credit score and yours has just been screwed up by them lowering your credit limit. It wouldn't suprise me if they now came back around and increased your interest rate because them lowering your limit lowered your credit score.

With credit scores being used to determine many things beyond credit these days -- including car insurance rates and getting a job, this must be very frustrating. Whatever happened to that credit card bill of rights? It seems like if AE agreed to provide you with a certain amount of credit at a certain interest rate that should continue to be the case unless you violate some terms of service...but I guess they can basically do what they want.