Dallas 1-wire Digital Thermo - issue with strong pullup
Why are you switching DSSTRONGPULLUPPIN high/low each time? Just leave it high all the time and change the pin mode only. Even if this leaves the ATMEGA's internal 20k&Omega; pullup enabled, this is insignificant with respect to the 4.7k&Omega; fixed pullup you have.

In particular, the sequence

pinMode(DSSTRONGPULLUPPIN, OUTPUT);
digitalWrite(DSSTRONGPULLUPPIN, HIGH);


is causing the the pin to be a strong pull-down briefly. This is probably creating the errors you are getting.