Hello everyone, with all these threads about the problem, I wanted to start a new one to make it clear, with all information you may need in order to help me out.
I've got a MacBook Pro '15 and an iMac 21.5', both are running (clean install) OS X Mountain Lion 10.8.2, both are up to date with the latest updates, both have the same apps, both have the same settings in "system preferences", and of course the same settings in "sharing" options.
My iMac is connected to my 5GHz network from my Time Capsule while my MacBook Pro use the 2.4GHz network.
Before going to bed, I leave both my Macs turned on, after 10min they go to sleep automatically. In the morning I can wake up my MacBook Pro from my iPhone or iPad with a screen sharing app.
The iMac doesn't respond at all. It stays in sleep mode. I can leave my MacBook Pro asleep for a week, it always responds. The iMac responds after a few hours but after 6 or 8 hours it seems to be completely asleep and doesn't respond to anything. If you think it's about the iPhone/iPad's app, when I try to wake the iMac from my MacBook Pro with "Back to my Mac" I have the same results.
I tried to connect my iMac to the 2.4GHz network: same problem.
OF COURSE "WAKE ON LAN" is activated in my system preferences.
I made a reset of the PRAM, the cache and the SMC on my iMac: same problem.
I type sudo periodic daily weekly monthly in the terminal and sudo dscacheutil -flushcache: same problem.
I tried everything I may have found in the forums or on this Support from people having the same issue: same problem.
I even tried to set the iMac with the same sleep mode as my MacBook Pro: same problem.
PLEASE HELP ME!