nova package install error

Hi,

I am trying to install nova from packages through nova PPA as per https://launchpad.net/~nova-core/+archive/trunk/. I am unable to install nova from the recent packages. Looks like its internally installing python-nova and is developing some file conflicts. Below is what I see:

root@node15:~/openstack# dpkg -l | grep nova
root@node15:~/openstack# apt-get install nova-common
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  powernap avahi-utils libnss-mdns libavahi-core6 ethtool libyaml-0-2 linux-headers-2.6.32-25 libtirpc1
  linux-headers-2.6.32-25-server libdaemon0 avahi-daemon python-yaml
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
  python-nova
The following NEW packages will be installed:
  nova-common python-nova
0 upgraded, 2 newly installed, 0 to remove and 19 not upgraded.
19 not fully installed or removed.
Need to get 0B/257kB of archives.
After this operation, 1,712kB of additional disk space will be used.
Do you want to continue [Y/n]? Y
WARNING: The following packages cannot be authenticated!
  python-nova nova-common
Install these packages without verification [y/N]? y
Selecting previously deselected package python-nova.
(Reading database ... 107462 files and directories currently installed.)
Unpacking python-nova (from .../python-nova_2011.1~bzr450-0ubuntu0ppa1~lucid1_all.deb) ...
Unpacking nova-common (from .../nova-common_2011.1~bzr450-0ubuntu0ppa1~lucid1_all.deb) ...
dpkg: error processing /var/cache/apt/archives/nova-common_2011.1~bzr450-0ubuntu0ppa1~lucid1_all.deb (--unpack):
 trying to overwrite '/usr/share/apport/package-hooks/source_nova.py', which is also in package python-nova 0:2011.1~bzr450-0ubuntu0ppa1~lucid1
Errors were encountered while processing:
 /var/cache/apt/archives/nova-common_2011.1~bzr450-0ubuntu0ppa1~lucid1_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@node15:~/openstack# dpkg -l | grep nova
iU python-nova 2011.1~bzr450-0ubuntu0ppa1~lucid1 OpenStack Compute - Nova - Python libraries

Could you tell me what could be wrong here. I tried installing two days ago, and it was working fine then with bzr revision number 440. Is there any specific way to download nova packages for a particular bzr revision number?

Thanks
Shiny