A friend (now a very good friend) of mine helped me out. Apparently the application speech-dispatcher was installed and somehow blocked the sound system. After removing speech-dispatcher everything worked fine.
For the record: This showed the problem
Code: Select all
$ sudo lsof /dev/snd/*
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
sd_espeak 1978 speech-dispatcher mem CHR 116,16 3288 /dev/snd/pcmC0D0p
sd_espeak 1978 speech-dispatcher 8r CHR 116,33 0t0 2663 /dev/snd/timer
sd_espeak 1978 speech-dispatcher 9u CHR 116,16 0t0 3288 /dev/snd/pcmC0D0p
sd_espeak 1978 speech-dispatcher 10u CHR 116,0 0t0 3318 /dev/snd/controlC0
sd_flite 1983 speech-dispatcher mem CHR 116,16 3288 /dev/snd/pcmC0D0p
sd_flite 1983 speech-dispatcher 14r CHR 116,33 0t0 2663 /dev/snd/timer
sd_flite 1983 speech-dispatcher 16u CHR 116,16 0t0 3288 /dev/snd/pcmC0D0p
sd_flite 1983 speech-dispatcher 17u CHR 116,0 0t0 3318 /dev/snd/controlC0
timidity 2184 timidity 6u CHR 116,1 0t0 2679 /dev/snd/seq