My iMac wont sleep

[mikey.c]

This has only just started yesterday, When I click on the Blue Apple on the top left corner and then click on "Sleep" my Mac goes blank then wakes up again within seconds.
There aren't any programs running as far as I know.

 

[NC MacGuy]

I've had the same issue since last round of software updates. Tried a bunch of things that have failed so have been just turning it off.

It does recognize the hot corner to go to sleep, just doesn't stay sleeping.

 

[GilesM]

I had the same issue as well after the latest software update, although recently it seems a little better but the sleep still does not work as it used to.
The only thing i changed was to remove my ipod from the iMac but I can't be sure this helped it may be a coincidence.