I'm using Sony Content Browser on a Mac (OS 10.8.2) and the File > Export > MXF for NLEs option, as well as several others underneath, is grayed out. Does anyone know why this would be the case? I'm trying to import XDCAM HD material from the PMW-200 to Avid MC 6.5 and testing workflows for the best method to do this.

If you're shooting XDCAM HD422 50Mbps in UDF mode, you already have MXFs. Just transfer them to your editing disk by dragging and dropping the contents of the card onto a new folder and use AMA to import them. The filesize limit on UDF is loose enough to use an entire 64GB card without splitting files.

Those options only apply when you're using EX 35Mbps MP4 in FAT mode. If that is what you're trying to import, and it's still grayed out, install the latest XDCAM browser rather than the bundled software.