Thanks for using Sitefinity!
Sitefinity does not yet boast full support for IIS8 or SQL 2012. However, we have instances of success. Take a look at this forum post. Namely the last post which discusses ensuring WCF is installed and enabled. It is apparently not by default. Since we use this service regularly it could be the root cause of your issues.
I hope this helps!
the Telerik team
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