Ask Mac Questions and Get Answers from Experts ASAP
First I need to ask the obvious question which is are you sure you did not accidentally type your pass in caps?
If you have tried that then you can just reset your password XXXXX starting from your OS X Install CD by holding the C key down as the computer starts.
From the Installer menu choose Reset Password XXXXX select your Mac OS X hard disk volume and chose your account then enter your new password XXXXX save.
Let us know if you need more info.