MAC screen query

[mckenzie]

any IT wizards on line please? Normally, if I have more than one application open at a time, as soon as I click on a screen it brings it to the front and puts the other open applications behind. Suddenly, it's not doing that and I need to physically move an application out of the way to get to a different one. Anyone know what i need to do to change this please? I'm on the Mac.

TIA

ignore my posting please. I've re booted and all is now fine.

Sounds like some had 'locked up' - I've got older iMac and eMac and would see the spinning ball if that happened, so would have to force a quit.