My mid-2011 MBA does the same thing when it's hooked up to the thunderbolt display. It's fine when I use it as a laptop but when I have it docked to the TBD it crashes every time it goes to sleep. Sometimes it restarts itself and sometimes I have to manually power it on.
I have been having problems with "random" shutdowns, although it's not isolated to 10.9.2, as I've had the same exact issue in 10.9.1
Sometimes, when I try to wake my computer up from sleeping, I have to manually power it back on, or I'm greeted with a grey screen stating that something went wrong and my computer was forced to restart. As you can imagine, this is incredibly annoying.
I was greeted with log of what happened after restart. I'll post it here in hopes that someone can help me address this issue.
BSD process name corresponding to current thread: WindowServer
Mac OS version:
Darwin Kernel Version 13.1.0: Thu Jan 16 19:40:37 PST 2014; root:xnu-2422.90.20~2/RELEASE_X86_64
Kernel UUID: 9FEA8EDC-B629-3ED2-A1A3-6521A1885953
Kernel slide: 0x0000000004a00000
Kernel text base: 0xffffff8004c00000
System model name: MacBookAir6,2 (Mac-7DF21CB3ED6977E5)