So you're saying that you get the "Library can't use both 'src' and 'utility' folders." error when you try to verify or upload a sketch but when you open and close Library Manager you don't get any warnings like that?
Library can't use both 'src' and 'utility' folders.
Invalid library found in C:\Program Files (x86)\arduino-1.6.6\libraries\Ethernet: Library can't use both 'src' and 'utility' folders.
The only one of those libraries I could find was TimerOne_v9 here. I installed it and didn't get any warnings and the only folder in it is examples. What unconventional folder do you have inside of your copy of that library?
I then tried removing the Ethernet, Robot_Control, SD, TFT, and WiFi libraries as suggested by Hillwalker.
hola a todos lo que encontré y asta ahora me a funcionado es que dentro de src se encuentra otra carpeta utility elimine la que estaba por fuera
Has this got something to do with the problem being discussed.
I am trying to install the f/m lcd library
Invalid library found in C:\Users\user\Documents\Arduino\libraries\arduino_75306: C:\Users\user\Documents\Arduino\libraries\arduino_75306