Blog started showing funny popups

I’ve a self hosted blog at
http://blog.mugunthkumar.com

From today, I see a popup frame (Add to Google Reader) that comes on certain pages. I tried changing the theme, it’s still not getting solved.
I tried disabling all the plugins, the problem is still there.

Can anyone tell me what’s causing that popup?

The frame redirects to http://blog.mugunthkumar.com/reader/link-frame
rather than http://google.com/reader/link-frame