I could start it in nightly on linux but with low framerate. On windows I see this in the console (and it stops at "preparing javascript"):

    [15:16:42.533] TypeError: asm.js type error: Internal codegen failure (probably out of memory) @ http://www.unrealengine.com/html5/UDKGame-Browser-Shipping.js:9649
    [15:16:50.798] out of memory