Since upgrading to Mavericks I am getting hangs of the Wakeup From Sleep function. The screen stays blacked out and the only way out is a hard reset (power off). It doesn't happen every time the MBA goes to sleep but has happened 4 times in the last 36 hours since I upgraded. It has happened on both battery power and A/C. I had ML for 2 months since purchasing the MBA in August and had absolutely zero issues with it... it's only since the Mavericks upgrade that this problem appeared. Anyone else had similar problems?