Yes, I was puzzled too. Normally they pull a film when it covers a subject made sensitive by recent news but neither wife nor I could think of a reason here.
Only guess is because news was extended to cover execution of Saddam Hussein, Superman would no longer fit in the slot allocated to it, so they dug out a film they have the rights to, to fit in the time available.
Often they say, either at the beginning or the end, "[because of....] there is a change to the advertised programme, and [Superman] will be shown at a later date."
Did this happen this time? Didn't happen to catch either the crucial beginning or end continuity announcements yesterday afternoon.