shadowbrush:
Hmm, interesting discovery, thanks for checking the code! FWITW though, I'm getting good readings on 4 MAX31855 breakout boards with this code. If this is a code issue, here is another MAX31855 library: GitHub - mcleng/MAX6675-Library: MAX6675 Arduino Library . I've tested it for Ryan's quad board: http://ryanjmclaughlin.com/wiki/Arduino_Thermocouple_Shield#Software .
I took a look at the Adafruit library for the MAX31855, and it does not have the protocol errors that the MAX6675 library has. So it should be good for multiple thermocouples.
Note that the MAX31855 and MAX6675 have different serial protocols, so you need to choose the correct library according to the chip you have.