From your answer to the private support ticked about the same problem I assume that the suggested solution worked on your side.
I am updating this thread for other customers that may experience this problem. Such errors are usually caused by incorrect installation of the OpenAccess' VS package and the first step should be to uninstall and install again OpenAccess. If this does not help, please let us know, so we can investigate your case in more details.
OpenAccess ORM Q2 2013 brings you a more powerful code generation and a unique Bulk Operations support with LINQ syntax. Check out the list of new functionality and improvementsshipped with this release.