BTW....I just finished a rework of some temperature sensor code that used an LM75 temp sensor chip.

This chip has an easy habit of locking up ending up holding the SDA line low as an output. The problem gets much worse if the LM75 is remoted off the microcontroller circuit board on the end of a long wires I2C bus to the sensor chip.and In many instances a power cycle off and back on is the only thing that resets the chip. I would recommend the TMP100 chip from TI ten to one over the LM75 chip.

Michael Karas