First MBA was a refurb. Worked great for about a month; shipped with 10.8.4 but updated to 10.9.1 then 10.9.2. The laptop would randomly shut down when I put it to sleep (regardless of closing the lid or choosing Sleep in Apple Menu) so that when I re-opened it, it was off, and had to use power button to reboot (it would load all my apps again but it was a full boot complete with startup chime despite volume being muted before). Problem persisted through numerous PRAM and SMC resets. Then started having very odd audio problems (would warble, lag, become staticky and unusable). Returned/shipped back to Apple and bought a retail (new) unit at the Apple Store instead. Just now, I was literally just sitting there, talking on my phone, staring at my computer screen, when suddenly the screen goes black. Laptop would not respond to lid opening/closing or even power-button. Had to hold command, option, P, R, then power button to even get the computer to boot. Similarly, it loaded my apps again upon booting but it was a full boot complete with start-up chime. What on earth is going on? I'm about to return this one and switch back to a Thinkpad. Is it Mavericks? Random shut-downs and reboots seem to be abound on the internet with Mavericks. Should I roll back to Mountain Lion? I'm getting exceptionally frustrated; this is literally about the worst problem a computer can have, especially a work computer; it is simply not stable or reliable in the least. Is there any way I can find crash logs or error logs? Or run diagnostic/hardware tests on my own without having to bring it into the "Genius" (read: hipster idiot) Bar? Any advice appreciated. ---------- Also, the most recent crash (new MBA), it didn't have any peripherals or even the adapter plugged in. Was at 98-99% battery. Just installed the SMC update.