Username and Password requested

This is the weirdest thing that has happened to my site. I am getting a weird message when I try to perform certain actions like approving comments or previewing a saved draft. It asks me for a username and password but my username and password don’t work!

Here is the complete message: A username and password are being requested by http://nirmukta.com. The site says: “Magic”

I have no idea what this means. Specifically, what the hell is “Magic” and why would my site ‘say’ that?

Has anyone come across this problem before? I couldn’t find support on this although I found a few others who have had this problem. They said it was a plugin interference, but I don’t use the plugin that was causing their problem.

Please help!!!!!!!!!