I2C hanging problem - 2 Arduino's and an 3.3V I2C Sensor TMP102

Hi, I was wondering if you or anyone has successfully connected 2 Ardunos AND a I2C 3.3 V sensor (e.g TMP102)

I can connect and communicate (using the Wire library) without problem 2 Arduinos (2 Uno's or 1 Uno and 1 Ethernet) or 1 Arduino with 5 Sensors. However whenever I try to connect 2 Arduino and 1 sensor the program hangs immediately (as observed via the printout in the serial-window stopping immediately upon connection)

I have tried with and without 4.7kO pull-ups.

All wires are very short, so capacitance should not be an issue.

I have tried in Master/Slave and Master/Master configurations.

I am Wire.read() the TMP102 temperature once per second so sampling should not be an issue

Even when the second Arduino has no communication code (like Wire.receive, etc) running. Simply connecting it's A4/A5 lines hangs the code on the first Arduino.

Any hints? I have banged my head against this for a while and searcher around and found "multiple Arduinos" and "multiple I2C sensors" but not "2 Arduinos and 1 (or more) sensors).

Thanks so much for any hint or advice, I'm truly at a loss here!

peter