I have installed Windows 8 PRO on my Asus UX31E (Zenbook) and sometimes happens that after I leave it charging after powering it off, I found it powered up (actually I found it in sleep mode because lid is closed). I thought that I forgot to power it off but I'm now pretty sure that wasn't my mistake after it happened already 5 or 6 times.
Is it a known bug or may be some setting that leads to that behavior? Ofc this wasn't happening on Windows 7.