Running Etoys-4.1-beta1-to-go on ubuntu lucid

Etoys crashes whenever I try to play a sound with the Sound Recorder I just recorded.

In the linux-shell this error shows up:

me@mybox:~/help/etoys/Etoys-4.1-beta1.app$ ./etoys.sh
sound: /dev/mixer: Input/output error
etoys: /home/piumarta/squeak/platforms/unix/vm-sound-OSS/sqUnixSoundOSS.c:355: dspOpen: Assertion `dsp->fd < 0' failed.
./etoys.sh: Zeile 93: 2093 Aborted $WRAPPER "$VM" -plugins "$BIN" $VMOPTIONS "$IMAGE" "$DOCUMENT" $IMOPTIONS