MacBook Air EFI Firmware Update 2.8
Apple has released MacBook Air EFI Firmware Update 2.8, which follows this week’s earlier update to the system management controller (SMC) for MacBook Air laptops (see “MacBook Air SMC Firmware Update 2.0,” 10 June 2014). For MacBook Air models released in the middle of 2013 and early 2014, this firmware update improves reliability when waking from sleep and when booting while certain USB and Thunderbolt devices are connected, plus fixes a rare memory issue that could cause the system to reboot. It also addresses a complex bug that prevented the built-in display from sleeping while connected to an external display and running Windows
using Boot Camp. As with other firmware updates, it’s best to rely on Software Update to ensure you get the right update for your specific model. Also be careful not to interrupt the update process! (Free, 4.8 MB, 10.8.5+)
I've been asking Apple to fix this sleep/wake problem for ages.....hoorah!