running instance on OpenStack Folsom release

Hello, I installed OpenStack Folsom on Fedora 18 according to the instructions I found on this website: fedoraproject.org/wiki/Getting_started_with_OpenStack_on_Fedora_18 but I encountered an error when trying to launch an instance. I googled a lot but I could not find anybody else who encountered this particular issue. My log file is the following: 2014-07-03 12:05:58 ERROR nova.compute.manager  [req-532d9f42-7132-41b7-ad20-3e1d26f4b3bc 1e5d1735d33c4e09845259bd83bd0b7e e9b017cc4ece4c33a8cb4df7fd1ff289]  [instance: 1b130e89-e37b-4d5c-9ea9-f2545e73d319]  Build error:  ['Traceback (most recent call last):\n', '  File "/usr/lib/python2.7/site-packages/nova/compute/manager.py",  line 503, in _run_instance\n injected_files, admin_password)\n', '  File "/usr/lib/python2.7/site-packages/nova/compute/manager.py",  line 756, in _spawn\n    block_device_info)\n', '  File "/usr/lib/python2.7/site-packages/nova/exception.py",  line 117, in wrapped\n    temp_level, payload)\n', '  File "/usr/lib64/python2.7/contextlib.py",  line 24, in __exit__\n    self.gen.next()\n', '  File "/usr/lib/python2.7/site-packages/nova/exception.py",  line 92, in wrapped\n    return f(*args, **kw)\n', '  File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py",  line 1101, in spawn\n    block_device_info)\n', '  File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py",  line 1942, in _create_domain_and_network\n    domain = self._create_domain(xml)\n',  '  File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py",  line 1920, in _create_domain\n    domain = self._conn.defineXML(xml)\n', '  File "/usr/lib/python2.7/site-packages/eventlet/tpool.py",  line 187, in doit\n    result = proxy_call(self._autowrap, f, *args, **kwargs)\n', '  File "/usr/lib/python2.7/site-packages/eventlet/tpool.py",  line 147, in proxy_call\n    rv = execute(f,*args,**kwargs)\n', '  File "/usr/lib/python2.7/site-packages/eventlet/tpool.py",  line 76, in tworker\n    rv = meth(*args,**kwargs)\n', '  File "/usr/lib64/python2.7/site-packages/libvirt.py",  line 2645, in defineXML\n    if ret is None:raise libvirtError(\'virDomainDefineXML() failed\', conn=self)\n',  "libvirtError: internal error no supported architecture for os type 'hvm'\n"] Any idea is kindly appreciated. Thanks a lot, Denis