According to a post on the XBox.com forums, Microsoft is delaying Scramble, the latest XBLA title, exactly one week. And in its place they will release the PGR3 Uno deck. Here's the post:

"As part of our Xbox Live Arcade Wednesday’s program, “Scramble,” the classic arcade side-scrolling, space shooter from Konami, was slated to go live tomorrow, Wednesday, September 6. However, during the final testing and certification of the title, we discovered some minor issues that should be addressed. Therefore, we are going to take an extra week and fix these items to ensure a high quality game experience for all when the title does launch on its new date of Wednesday, September 13. Until then, we have a new bonus release going live tomorrow - the new Project Gotham Racing 3 theme deck for UNO will be making its debut."