I'm still having this problem. I'm on an iMac, operating system is OSX Yosemite v10.10.3, browser is Safari v8.0.6. This does not happen when I'm browsing through the Marketplace "What's New," but it's happening when I'm looking at the vendors pages which have sales. The screenshot I took was when I was looking at Mihrelle's store, and it also does the same thing today (Aug 31st) when browsing through 3-d-c's store. The window appears shortly after I start scrolling down. I can get rid of it by scrolling back up to the top, but it always appears when I scroll down and blocks the view of the third column. Hope this helps. Thanks for the quick reply.