guys need some help on my imac, since the last update 10.6.4 the sleep has gone to pot ie it will not stay in sleep mode, if i wait for the 5 or 10mins that i set it to in energy saver it comes back on in a few minutes after it has gone of, also if i go to the apple menu (top left corner) then force the sleep it takes about 15-50 secs to go of but its back on again an a few more secs. starting to do my head in on a night as its coming on and of with nothing happening on the mac ie nothing open or downloading 
