I’ve heard a lot of complaints today about Windows Live users being subjected to frequent pop-up ads taking them to the Windows Live Essentials download page. I haven’t seen it happen personally, but Microsoft has now acknowledged that the issue exists. Via a spokesperson, I’m told:
“We are aware that some Windows Live Messenger customers may be experiencing an issue where Messenger automatically launches an unneeded webpage, and we are currently investigating. We are working aggressively to address and fix the situation once we isolate the cause. We sincerely apologize for any inconvenience this may be causing our customers.”
One temporary workaround is to place rad.msn.com in the Restricted Sites zone for Internet Explorer. You can find the instructions in this post on a Microsoft-run forum.
Ed Bott (@ wordpress.com) 
I run Live Messenger 2011 on multiple computers and I haven’t see it either. I believe it happens, but I’m curious what’s going on.
My MSN Messenger pops up whenever I boot up the computer. How do you get these things to stop?