Just doing a follow up in case anyone reads this for the same problem we had. In my case the problematico module was gsitemap. BTW, it's quite easy to find the problematico module: just start deleting them one by one and checking the modules page. When you delete the problematic one all of the remaining modules will appear. From that point, just restore the modules you deleted except for the one that was causing trouble. All of your configurations will remain unaltered.