I have noticed a rather odd trend with Encore. I have successfully used it on my Mid 2012 Mac Pro with 10.9.4 for some time now, and it's been great. I also have had it on my Macbook Pro Retina, and it worked fine on that machine as well. I have it through the CC license and I have an additional CS6 Production Premium license.
I loaded Adobe CC on my HP PC with Windows 7 Laptop-- downloading the CS6 version through the CC site. and it always crashed on startup, never really ever loading up at all. Same problem on my Macbook Pro 13" with 10.9.3. Crashes at startup. I just loaded the CS6 Mac version on a Early 2008 Mac Pro tower, running 10.9.3 and the same issue. Crashing at startup.