Don't get me started on the fact that we use MSN Messenger (though we are switching to a paid product we can control!). This morning I came in and MSN Messenger was freezing, with the CPU pegging to 40%. I uninstalled it, reinstalled it, and was still having the same issue. The odd thing was not all of us were having the issue (or at least not everyone was reporting it). I decided to go third party since a lot of people request help via Messenger. As I was sitting at my desk it was still ticking me off that there was an issue at all and since my boss is out tomorrow I didn't want to get swarmed with reports of the issue. Via trusty Google I entered "msn messenger using cpu" and found a site describing the issue to a t (including the 40% cpu usage).
The author details that Microsoft serves it's adds via rad.msn.com and that this is what was pegging the CPU. He added to the Restricted Sites list in Internet Explorer and the issue was resolved. Tried it on my PC, issue resolved. Try it on one of the Web Developers PCs, issue resolved. Fired up Group Policy Management and added it there. GPUpdate, restricted site added and suddenly people start popping online. Thank you Google!
How to Fix Windows Live Messenger 2011's High CPU Usage | Technology Mob | Technology Mob