WP.com Stats Erratic behaviour

In less than 24, of nothing having having changed on the site, I get this strange behaviour from WP.com stats plugin. I checked my stats about 22 hrs ago and wanted to see them now. But this error is very peculiar.

This is what happens. I log in to my wp-admin. I see the dashboard. Click on Site Stats under Dashboard menu … it takes a couple of second, then shows me log in screen. With the menu still visible and working. Plus a BIG Word Press logo where it should be saying view site in text on top left corner.

I did first aid. Deactivated and activated the plugin. No use.
Please help.