Sorry Jules, but a single error message in German is not much to work
with - at least not for me. You can try to rebuild in debug mode and
that may give some indication of where the problem occurs, but please
try to switch language to English before running.
Did you you test your gnuradio installation to see that it is working properly?
Which device are you trying to use? USRP, FCD, rtlsdr??
I can confirm that the latest gqrx from git works using the latest
gnuradio, rtlsdr, amd gr-osmosdr code on Xubuntu 13.04.
Alex