At what point does it fail? The download process is the same regardless of whether you choose audio only or video. The only difference is that the audio stream is extracted and saved, then the video input file is deleted (if extraction is successful). Also, do you have the latest version installed (0.3.6). It's only been in the repos a short while. I've actually just finished downloading as an audio file, and it worked fine. Try running from the x-term: Code: run-standalone.sh /opt/usr/bin/qmltube Check the output for any errors. You can ignore any warnings about QNetworkConfigurationPrivatePointer.
run-standalone.sh /opt/usr/bin/qmltube