blue screen

Imac 2.93GHz Intel Core 2 Duo when closing down my computer goes to a blue screen and is not shut down just a spinning wheel .
have to close by pressing and holding start button.
happens with some open programs on the desk top ( Microsoft Outlook )
Eddie

How much time are you giving it? Give it 10-20 minutes and see if it changes. That one time you wait could save you time later.

eddir

all night, the next day i have to press the keyboard and the blue screen is still going ,nothing happens till I shutdown by rear button , and restart again