Known issue: http://forums.adobe.com/message/4265437
Btw, ACR7 from Photoshop CS6 beta seems to match Lightroom 4 perfectly.
And it won't be released for Photoshop CS5. As soon as a version of Photoshop is released, support for the previous versions ends. There is a ACR 6.7 RC available on that Adobe Labs web site. It is compatible with CS5. It will read all of the adjustments made in Lightroom 4.1. However, although it will read all of the adjustments, you cannot do the new adjustments as you will be able to in ACR 7. That means sending images from Lightroom as smart objects will not give you access to all the new features of ACR 7.
North America
Europe, Middle East and Africa
Asia Pacific