Solved.
Netlogo 7.0, as it loads the widgets from the previous version into the new Interface, changes the value of a "eta-bending" slider global variable being called in the reporter procedure to zero, resulting in all zero raw-eta values.
And no, I had not accidentally changed it myself. I just closed and reopened the file in Netlogo 7.0 (by saying yes to accepting to resize widgets) and Netlogo 7.0 reset again the value of the "eta-bending" slider global variable.
It did not do the same with other slider global variables (maybe because this variable had a small increment step set to 0.001? I don't know)
Anyway: You may want to check all you widget values after you open in Netlogo 7.0 a model you had written on a earlier version.