Unable to change focus options with Sigma 18-200 mounted

Up until two months ago with my D5100 I could select whatever focus option I chose with any lens. Starting two months ago, when my Sigma 18-200 is mounted the mode is Manual focus, and the focus mode selection option is grayed out so that I can't change it. When I mount my Nikon 50 f1.4 things are as they should be.
I'd appreciate your thoughts

Sorry guys. As is often the case, asking the question gave me the answer. In filling out the profile for this forum when listing lenses I came across my new version of the Sigma 18-200 which has no problem with focus modes. I didn't realize that I had switched the two 18_200s.