I have the exact same problem and have had since last week.
My blog is TheNewJew.wordpress.com and I use Mozilla Firefox as a browser (don't know if this matters).
The top of the screen is normal, but under the title of the top post, the rest is gray with a tiny smiley face resting on the white-gray border. The sidebar as fallen to the bottom side.
Additionally, I was looking at different themes on WordPress' presentation options today and every theme where there was supposed to be a sidebar appeared with the sidebar fallen to the bottom.
Obviously this is very disconcerting.
I am posting here as the topic is related in hopes that someone can help me. There is no one thing that I did out of the usual for it to happen, it just started one day when I posted as usual. (Nothing new downloaded, regular virus scans coming up clean, etc.)
Help would be very much appreciated.