To put a cap on this; it seems to be the lens that is causing my problems. I was using my Sigma 70-200 last night and it lost communication with the camera at least a half dozen times during the shoot. To get everything back working I would have to either re-mount the lens or shut the camera off and re-mount the lens. Very annoying to say the least. Since this is the only lens that I am having this problem with, it will be sent back to Sigma for repairs. Lens is still covered under warranty, thankfully.
Thanks to all that commented on this, especially Russ. I likely would have found the problem but the suggestions here shorten that time frame.