I am also having issues with a 49 port hub on Mac OS X. Both 10.7 and 10.9 on two different computers.
I am waiting on another PS to make sure it is not causing problems. I doubt it though as it was bought new (5v 38amp) and I do have two fans running on the 12v rails.
Have swapped out usb cables and moving miners around from 49hub to regular anker hub to narrow down problems.
I narrowed it down to the power supply not putting out enough 5v amps. Even though it was rated for 5v 38A !!!!
Some of the confusion was that on them mac at least using an anker hub at same time as the 49 port caused issues. Once I moved the anker off then reduced the amount of miners down to 35 no problems. I even walked them around the ports to be sure that ports were not bad.
While one of the first things I tried was reducing miners down to just 7, the anker was still attached and causing issue. Brain fart and violated first rule of trouble shooting. Change only 1 variable at a time.
So I guess PS labels are like clothing tags. Sort of semi accurate not. Gotta love that labels don't mean sh*t!!!