Okay. I'm trying to record a Skype call (screen, microphone and 'stereo mix') by using avconv (ffmpeg) and arecord.

The commands I am using are: (in a script, of course)
avconv -v panic -f x11grab -s 1600x900 -i :0.0 -r 30 -vcodec libx264 -crf 0 video.mkv &
arecord -D pulse -f dat audio1.wav &
arecord -D pulse -f dat audio2.wav &
PulseAudio is configured correctly to make the first arecord record the microphone and the second record the 'stereo mix'.

If I run the program on Firefox, while I'm playing a YouTube video, everything works properly.

If I run the program, then initiate a Skype call, Skype complains about a 'Problem with Audio Playback'.
If I initiate a Skype call, then run the program, I get about 3 seconds of audio on each of the files, before they abruptly end. No error messages are printed to the console.

Can someone help me?
Thanks in advance.