Ok, I know it's stupid ..
Maybe, maybe not, it would be great if one could use a single pin for 2 different functions.
The closest I did was to use the serial port for 2 different devices (one input one output) but that are two pins.
OK back to the problem.
The LCD pin seems to act as an additional pull up/down resistor. (I assume the LCD is also connected to 5V and GND)
That is confirmed by the fact that if you remove the LCD the DS doesn't work any more.
What is the length of the cable to the DS? this affects the resistor to choose, the longer the cable the smaller the R.