Installing plasma-mobile breaks plasma-desktop

I've tried plasma-active by installing plasma-active and some related packages.
After installing I found something wierd as following:
* Login with plasma active session will eventually give me a black screen and a pointer (no background, or any UI).
* Login with plasma desktop session will end with a desktop version of loading animation and an "plasma active" UI.

then I remove plasma-active related packages
* Login with plasma desktop session will end with no plasma-desktop UI (I have to manually execute it), kWin seems to work though.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: plasma-active (not installed)
Uname: Linux 3.4.5-intelcore2optimized-vdragon-mod x86_64
ApportVersion: 2.0.1-0ubuntu11
Architecture: amd64
Date: Sat Jul 21 06:49:45 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
SourcePackage: plasma-mobile
UpgradeStatus: No upgrade log present (probably fresh install)