Why does OS X 10.7.5 ask for a password at each startup?

Hello everyone out there! I've searched the Support Communities and have not found an answer to my issue. I have an external HD that I recently updated to OS X 10.7.5 (from 10.6.8) using the Internet system that Apple has (command-R at startup to access the Apple Utilities) and now at every startup it asks for password: "AppleIDAuthAgent wants to use the keychain, please enter the password". I know the password, but I want to know how I can make it stop asking for the password. Thanks!