T-Mobile Phone IM Messenger Application Errors?

I have a T-Mobile cellphone and I use to go on AIM on it, but recently, I can't sign on. It kept on saying Application Error, and when I click Details, it says Illegal Access Error: java/lang/IllegalAccessError: Cannot access calss com/nokia/mid/ui/lcdui/DisplayStateListe… from cl ao. Can someone please help?! THANK YOU~!