[Users] Configure NFS resource from Host

Hello everybody, I'm trying to configure and install oVirt for test in our University faculty. I have installed an engine an a host, both of them with Fedora 17. The engine is working and I can log-in in the Data Center with admin user. I have tried to add my host to the data center portal and I successfully done. After that I have tried to add a NFS resource which is in the host that I have added. If I open a console in the engine and log-in as vdsm user, I can mount the NFS resource without problems. The problem is when I tried to add this NFS resource to the Data Center. I have followed the tutorial http://www.ovirt.org/Quick_Start_Guide#Configure_Storage, but when I have completed the form and pressed "Ok", after one or two minutes I receive one screen with bellow error: "Error: A Request to the Server failed with the following Status Code: 500" I'm attaching the vdsm.log file with the lines that are created with this operation. I hope that someone can show me what is the problem. If you need more information aboout the installation I can show it. Many thanks in avanced, Juanjo.