Could you explain this any further? I recently replaced this because of a bad microphone and now the proximity sensor isn't working. I transferred the plastic/rubber gasket/bracket thingy over. I've disassembled and reassembled the thing 3 times to make sure the sensor is properly seated, no luck. The ambient light sensor for auto brightness works just fine, which I think is actually the one with the plastic part, unless I'm missing something?
Is it possible the new cable assembly just has a bad sensor?