Similar to this user (https://forum.solidworks.com/message/216879#216879), I seem to be missing that option as well. I'm new to Simulation with respect to composites. I'm trying to work through some resources I found online, but without the "Composites" option in the property manager, I'm pretty much at a stand-still.
I'm running SW 2011 64-bit on Windows 7. My current licenses are SolidWorks Premium and SolidWorks Simulation Professional.