.......all right, neither do I ! But anyhow - my wives Penryn MB does ! I mean, after 10 minutes of inactivity. Ive started this new thread since my last one was starting with a confusing title, sorry, but basically its still about the same: My MBA does definitely not go into sleep mode after the respective time of inactivity as set up in the system preferences for energy saving! The screen shuts off, yes. But hd and cpu they keep working, and the white LED on the front remains constantly bright. That's not what I would understand as sleep mode.. Ive tried quite a lot to sort this out, including a re-format with fresh install of OS X this morning: But even with nothing than a naked OS and standard settings it was still the same: no time-tiggered sleep mode! This is kinda weird to me since the MBA goes into sleep mode without any trouble when I close the lid! So I would believe it couldnt be hardware related. But now after the fresh reinstall it neither can't be software related, can it? Any idea? I am not too familiar with macs, not yet . However - many thanks!!