Seems like there is a major problem going on with WordPress.com and it’s stats plugin right now. On logging into your WordPress blog, instead of seeing the pretty charts and stats, you will see a login box instead. On logging in, it just redirects back to the same thing again (Dashboard with login page). And if you try logging into your profile over at WordPress.com, then it just redirects back to your main blog associated with your WordPress.com profile even if it is a self hosted blog.
It might have to do something with the new sexy stats that WordPress guys were scheduled to be rolling out. I hope the problem gets fixed soon.
Update: Looks like WordPress guys are looking into it.
Update 2: The problems seems to have been fixed by WordPress staff. Good work, guys.