It sounds different from the normal unity theme, how to correct it?
Why are the images changed?
It happens even though I have booted few times.
Looks like gnome-setting-daemon is not running or is hanged.
To solve it just open a terminal and type
The first line should kill any instance of gnome-settings-daemon that is running, just in case. The second line should launch it.
If this works, we know the problem and a workaround, now we still have to discover why it isn't running.