Update: on April 10, 2010, Microsoft Released an Update to Support OCS 2007 R2 on Windows Server 2008 R2, for more information, refer to this link
So, you’ve been trying to install OCS 2008 R2 on Windows Server 2008 R2, well, unfortunately, it is currently not supported. although you will find some geeks on the internet who managed to work it out and install it (Actually it installs and works for non-edge facing deployments), I Highly recommend you not to do so, as you will face many issues with the Edge server.
The Event Viewer on the Edge Server will report an error indicating that the certificate provided by the front-end server is not supported (although it is!)
After spending more than 48 hours trying to work it out, it didn’t 
, i ended up reinstalling Windows 2008 R1 and installing OCS R2 on it.
Buttom Line, Don’t waste your time, when Microsoft supports it, go for it, otherwise, stick up with Windows Server 2008 R1 for your OCS R2 Deployment.