I'm a WordPress novice trying to help a friend (who is even more of a WordPress novice) with his WordPress blog hosted on GoDaddy.
It was working fine until he apparently (he doesn't fully remember) was prompted to upgrade the software.
Now the blog still works for end-users (you can see it here) but whenever you log into the WordPress admin, you get a Page Not Found / "This is somewhat embarrassing, isn’t it?" page. The URL that the browser has been redirected to is:
It seems like the upgrade attempt was messed up somehow. Given I don't know what precisely caused this, what steps should I take to start investigating the problem and ideally rolling back the upgrade (or completing it) so that the blog is usable again?