While everyone is complaining about the display of version number in security center, I found another problem.
I had created silent installation in my lan computers running 4.5.
While the program has nowbeen updated to the new version in all the lan machines, I find the splash screen remains the old one and in the about avast the version number is shown as 4.5.603.
In my host machine, however, which runs xp home, the splash screen and the about box displays things correctly.