Ok, new theory
the error occurs at the following line :
T 0 2600 -2472 56 0 1 0 "The four "TOP" pads have to be connected to the top layer with thermals.\nThe top layer under the device has to be connected to gnd with several vias for low impedance." Normal 0 C C
The string contains embedded quote marks, which is not allowed. I would say that is a bug in the conversion script "eagle-lbr2kicad-1.0.ulp Version:2.70". Quote marks must be escaped with back-slash "\".
After applying that fix to the lib file via a text editor, the library loads better (still has warnings, but can be ignored) in the latest nightly build (2017-02-12).