A liquid crystal display (LCD) includes a plurality of gate line drivers that are to be sequentially activated during a display frame in response to an input vertical synchronization start signal having a predefined waveform. However, during shift of display mode it is possible that the vertical synchronization start signal will be asserted more then once in a frame and cause a problem. The LCD includes an error detecting and blocking unit which detects when the vertical synchronization start signal is asserted more then once in a frame and blocks the second assertion from being passed forward during the one frame so as to erroneously reactivate the plurality of gate line drivers a second time during the same frame.