Needed to log back in to update my reply. As I mentioned in my previous post, I had the same problem with my feet and shoes bases. I did attempt to reset my cache as someone suggested, but it didn't help. I uninstalled and reinstalled the SL viewer, and thought it made a difference...but not really. I discovered that I'd made a change to my in-world graphics in Preferences. Preferences > Graphics > Quality and Speed setting. I noticed that I had increased that setting from High to Ultra. That is what caused the problem with my feet not working with the shoes bases. When I dropped the setting to High, the problem went away. Strange but true.