You're trying to record 60 fps?? Dude, no wonder.
That will probably kill most systems out there.
Remember, you're not just "rendering" 60 fps... you're rendering 60fps, analyzing each and every frame, adding said frame into a file, and compressing said file. It's not just a video function, it's using a heckuva lot of CPU, RAM, heck, the entire system to do that.
What's the result if you drop to half screen size and (let's make an example) 15 fps?