Just to be sure: When you say the visuals are late compared to the audio output, do you mean the position of the play cursor as it moves across the waveforms on the tracks?
Is it a constant delay, or does the delay increase as playback progresses?
Please check that the samplerate in the arrangement properties dialog is set to 48000. Changing the default samplerate in the interfaces dialog will not affect the samplerate setting in arrangements that are already created.