It kept rebooting the whole server when it said "Starting Windows"
I am having this same problem. Would you mind sharing what you did to resolve the issue?
I am installed SBS2011 but it is based off of 2008R2 so the issue is most likely the same.
I managed identify the issue. The system I have was configured with 24GB of RAM. Removing two stick enabled it to boot into the installer properly and thus push through the installation. Once completed and into Windows I was able to add the additional RAM with no issues.
So it appears the issue was related to RAM either the amount or the configuration. Hopefully somoene will find this post beneficial.