I FOUND THE SOLUTION: PLEASE DELETE THIS MESSAGE!
The builtplate of my 1 week old Ultimaker2 won't raise properly. It only raises about 8 cm, then stops.
Everything worked just fine yesterday.
Today I wanted to fine tune the builtplate, and started the procedure. When the builtplate was raised to begin with, it stopped short by about 2 cm from the nozzle (when it asked me to adjust it to 1 mm from the nozzle, which evidently wasn't possible).
After that I raised the builtplate by going to the Advanced settings. It then stopped even further down. And subsequent attempts onl