Quantum-server doesn't start

my guess would be that you have an old version of the python paste deploy library.

how did you upgrade/install quantum?

it may be enough just to use pip to update dependencies using the tool/pip-requires file by running the following within the quantum directory

sudo pip install -r tools/pip-requires

I did that...and I suppose this is the problem: I mean there are some dependancies problems
this is what I did
wget https://launchpad.net/quantum/folsom/2012.2/+download/quantum-2012.2.tar.gz
tar xf quantum-2012.2.tar.gz
cd quantum-2012.2/tools
pip-python install -r pip-requires
cd ..
sed -i 's/quantum-l3-agent = quantum.agent.l3_nat_agent:main/quantum-l3-agent = quantum.agent.l3_agent:main/g' setup.py
sed -i '128a \\tif self.conf.use_namespaces:' quantum/agent/l3_agent.py
sed -i 's/ self._destroy_all_router_namespaces()/\t\ \ \ \ self._destroy_all_router_namespaces()/g' quantum/agent/l3_agent.py
sed -i 's/def wait(self, check_interval=0.01):/def wait(self, check_interval=0.01,timeout=None):/g' /usr/lib/python2.6/site-packages/eventlet/green/subprocess.py
python setup.py install

I need to rollback everything bu I don't know how

how about this command:
gongysh@gongysh-laptop:~/git/quantum/tools$ sudo pip install paste --upgrade
Downloading/unpacking paste
  Running setup.py egg_info for package paste

    warning: no previously-included files matching '*' found under directory 'docs/_build/_sources'
Installing collected packages: paste
  Found existing installation: Paste 1.7.5.1
    Uninstalling Paste:
      Successfully uninstalled Paste
  Running setup.py install for paste
    Skipping installation of /usr/local/lib/python2.7/dist-packages/paste/__init__.py (namespace package)

    warning: no previously-included files matching '*' found under directory 'docs/_build/_sources'
    Installing /usr/local/lib/python2.7/dist-packages/Paste-1.7.5.1-py2.7-nspkg.pth
Successfully installed paste

I fixed the problem by reinstalling all the dependencies with easy_install and not with pip.
But unfortunately when I start the ovs agent, I get this issue:

INFO:__main__:Agent out of sync with plugin!
2012-12-06 10:24:15 INFO [__main__] Agent out of sync with plugin!
DEBUG:quantum.agent.linux.utils:Running command: sudo quantum-rootwrap /etc/quantum/rootwrap.conf ovs-vsctl --timeout=2 list-ports br-int
2012-12-06 10:24:15 DEBUG [quantum.agent.linux.utils] Running command: sudo quantum-rootwrap /etc/quantum/rootwrap.conf ovs-vsctl --timeout=2 list-ports br-int
ERROR:quantum.agent.linux.ovs_lib:Unable to execute ['ovs-vsctl', '--timeout=2', 'list-ports', 'br-int']. Exception: wait() got an unexpected keyword argument 'timeout'
2012-12-06 10:24:15 ERROR [quantum.agent.linux.ovs_lib] Unable to execute ['ovs-vsctl', '--timeout=2', 'list-ports', 'br-int']. Exception: wait() got an unexpected keyword argument 'timeout'
DEBUG:quantum.agent.linux.utils:Running command: sudo quantum-rootwrap /etc/quantum/rootwrap.conf ovs-vsctl --timeout=2 list-ports br-int
2012-12-06 10:24:17 DEBUG [quantum.agent.linux.utils] Running command: sudo quantum-rootwrap /etc/quantum/rootwrap.conf ovs-vsctl --timeout=2 list-ports br-int
ERROR:quantum.agent.linux.ovs_lib:Unable to execute ['ovs-vsctl', '--timeout=2', 'list-ports', 'br-int']. Exception: wait() got an unexpected keyword argument 'timeout'

are you using RHEL? It may be related to this: https://lists.launchpad.net/openstack/msg02565.html

Yes I'm using CentOs 6.3. I checked the file and the timeout parameter is already there.
This is the error traceback

ERROR [quantum.agent.linux.ovs_lib] Unable to execute ['ovs-vsctl', '--timeout=2', 'list-ports', 'br-int']. Exception: wait() got an unexpected keyword argument 'timeout'
^CTraceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 828, in <module>
    main()
  File "/usr/lib/python2.6/site-packages/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 823, in main
    plugin.daemon_loop(db_connection_url)
  File "/usr/lib/python2.6/site-packages/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 782, in daemon_loop
    self.rpc_loop()
  File "/usr/lib/python2.6/site-packages/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py", line 775, in rpc_loop
    time.sleep(self.polling_interval - elapsed)
  File "/usr/lib/python2.6/site-packages/eventlet-0.9.17-py2.6.egg/eventlet/greenthread.py", line 30, in sleep
    hub.switch()
  File "/usr/lib/python2.6/site-packages/eventlet-0.9.17-py2.6.egg/eventlet/hubs/hub.py", line 177, in switch
    return self.greenlet.switch()
  File "/usr/lib/python2.6/site-packages/eventlet-0.9.17-py2.6.egg/eventlet/hubs/hub.py", line 226, in run
    self.wait(sleep_time)
  File "/usr/lib/python2.6/site-packages/eventlet-0.9.17-py2.6.egg/eventlet/hubs/poll.py", line 84, in wait
    presult = self.do_poll(seconds)
  File "/usr/lib/python2.6/site-packages/eventlet-0.9.17-py2.6.egg/eventlet/hubs/epolls.py", line 61, in do_poll
    return self.poll.poll(seconds)