UE Editor crashes when I open it on iMac

I have one iMac 27 inch.
Processor 2,66 Ghz Inte Core i5
Memory 4GB 1067 MHz DDR3
Graphics ATI Radeon HD 4850 512 MB
Software OS X 10.9.3 (13D65)

I installed UE4. When I click in Launch, the UE Editor opens and crashes. How can I fix this problem to start to use?

Thank you very much!

You could try looking at the log file in Unreal Projects\MyProject\Saved\Logs which may give you an indication of what happened when it was trying to start up. Change MyProject to whatever project you were loading at the time.

Your Mac is under-spec. the minimum requirement is an AMD 6870, which is significantly newer than your ATi 4850 which only supports OpenGL 3.3. Unfortunately the Mac drivers for the 4850 also lack support for some necessary rendering features which UE4 relies upon. These have been worked around for the forthcoming UE4 4.2 release and so when that update is released you should be able to run the editor on your Mac, however we don’t officially support your GPU so performance may be low.