I have the same problem, but with diferent websites. Every once in a while, yahoo.com and dallascowboys.com give me the mobile version. this has happened with these two sites on 2 different computers! I have to go to internet options and "delete all" to fix it. But it will start happening again a couple of weeks later. I am using IE7 on Windows XP pro.
I'm using IE 8 with vista and mcafee virus protection. I'm not using any added toolbars that I'm aware of. When I try to go to mcdonalds.com or redlobster.com, it redirects me to the mobile version of the site. Those are the only two sites with the problem. It started a few months ago so I'm not sure what I installed or changed that made it start happening. I tried deleting history, accepting all cookies, and putting the mobile version in the list of restricted sites and nothing helped.
I did download firefox and was able to view the regular sites with it, but I normally use IE so I would like to get it working correctly if possible.