>I record my voice OK, but when I press Play, it plays only a small segment
>of what I said, then it skips to near the end.
I've got an old netbook running Ubuntu 11.10, running OpenJDK, and tested this and I was able to record/playback and upload a submission... so it should work
Are you using a USB microphone? Ubuntu defaults to your analog audio port, so that needs to be changed to point to the USB mic.
Please post a copy of the Java console output after you try to record and play a prompt.