Haloing around windows - what's going on?

Hi everyone. I'm using a Canon 5D and have recently been experiencing some pretty bad haloing or light creepage around windows when shooting interiors.

I'm not sure if this is a camera problem or a settings problem as I can't remember this happening in the past. It's most noticeable when there is a drastic contrast difference between outside and inside (sunny days and dark interiors). I have fiddled with settings but to no avail. Attached is an example of the problem I am getting around windows. Could any of you good people provide me with a possible explanation as to what is going on?

Settings for this shot:
f11, 100 ISO, Canon 17-35 lens.

HTTP response: NOT FOUND | MIME changed to 'text/html'

Do you have a filter on? Is the front element clean? Is this a non processed image? Can you post a little bit bigger crop of the window?