I2C Barometric Pressure Sens. stop as soon as SI7005 Humidity physically connect

BPM 180 (or for that matter 085 0r MPL3115A2) stop sending data to serial as soon as Humidity sensor SI7005 is electrically connected to I2C., even before uploading any code. I disabled the pull-up resistors on BPM085 but with no success. I have no idea what the problem might be Thanks in advance for anybody's help!