I authorized my computer, but when I try to install an app, it doesn't recognize that it is authorized. How do I fix this problem?

I chose Store>Authorize this Computer, and it accepted it. It shows when I go into my account, that my computer IS authorized. But when I try to install and App, it keeps telling me that I need to Authorize my computer, and won't allow me to install the app. I've consistently tried to authorize, but it IS already authorized...driving me nuts. How do I get my app installed when itunes won't even recognize that it is authorized???