Resetting I2c Address - MLX90614
Page 13 of 35 in the datasheet states:


  In order to provide access to any device or to assign an address to a
  SD before it is connected to the bus system, the communication must
  start with zero SA followed by low RWB bit. When this command is sent
  from the MD, the MLX90614 will always respond and will ignore the
  internal chip code information.


Supposedly, all you have to do is to connect only one device and use the address zero to read/write the registers.