Software Deployment

Hello,
I have a big problem since several days and I don’t manage to find the reason of it and I neeeeed your help ;-)

I am trying to deploy an msi package that I did (that first copy files into program files, and then launch an exe with argument).

I have configured my program like that :
General :
Command line : program.msi /qb
Start in : c:\
Run : Normal

Environment :
Program can run : only when a user is logged on
Run Mode : Run with administrative rights (and allow users to interact with this program) (to let me see if there are errors)
Drive mode : Run with UNC name.

When I am watching my client logs (execmgr.log) I have that :

Command line = "C:\WINDOWS\System32\msiexec.exe" /i "C:\WINDOWS\System32\CCM\Cache\FR10000D.1.System\program.msi" /qb, Working Directory = c:\

Here it is for my configuration.

Now, when my program is advertised and ready to launch I have an alert box saying :
"unable to install because a newer version of this product is already installed” and in my log file I can read :
'Script for package...failed with exit code 1603'

Moreover, if I start manually my program from the command line prompt (from the client too) I don’t have such message and my program runs and installs successfully.(and I precise with exactly the same command line as noted above)

Please could you advice me about that problem that makes me crazy for several weeks ?
I have made a lot of tests but for the moment it doesn’t work.

Thanks a lot.

P.S:Sorry if I make mistakes but I am not english ;-)