I don't recognize that alert. I'd look to some other external influence.
The wording in the message and the fading of the page is what makes me think it's the site itself. Under the menu bar of the "about IE box" I had open, there was a link to click to ignore the message and once I clicked it, the page faded in without any problems.
Also I only had one tab open and store page is a secure site, which rules out an ad pop up.
When I go to the site now, the page opens correctly. Probably just a glitch but I thought it best to mention it.