Hi!
How can I set the gamma setting at KDE startup (4.5)?
every time I restart kde it resets to the initial values (1.0)...

the setting should be saved in ~/[.kde|.kde4]/share/config/kgammrc

after you make the change in systemsettings does the file reflect it? If not try to manually edit the file.

if the file is written correctly and at restart it reverts to the default then it would be a bug and should be reported to bugs.kde.org

I think it's a bug....the file is written correctly but at restart the system setting show me a different value.