What module is in that position? If it is one of our older modules (such as JFBCLike, etc) that has been deprecated for a couple of years now and no longer supported as of 6.5.X, you can encounter that error. We still supported sites that were using the older modules, but we had to make some changes that broke it in the latest release. If that's the case, you should be able to replace the module with the SCSocialWidget configured as Facebook provider and the desired widget. Those should render the exact same thing as the old module. The SCSocialWidget has been the new module to configure all of the different social widgets from a similar interface.
-Melissa