Hi guys,
first the good news: pd does work in ubuntu. (I had exactly the same problem two days ago) A fresh install of Ubuntu-Hoary is missing the 'snd_seq_oss' module. try: 'lsmod | grep snd' to find out. then 'sudo modprobe -i snd_seq_oss' (if it's missing) now try pd. Don't forget to disable all sound in Gnome ( system/settings/audio, deselect 'start sound server with gnome') If it's now working, you need to make the changes permanent: I use a tool called 'modconf' to do so. It's not in the ubuntu repositories, download it from any debian-mirror. Reboot to make sure youre in an initial state, otherwise 'modconf' will tell you that 'snd_seq_oss' is installed an therefore won't do anything. Do 'sudo modconf' scroll down to '/kernel/sound/core/seq/oss', hit enter. select 'snd_seq_oss', hit enter; no special parameters required. Now exit. You can use the version of pd thats in ubuntu, or the (slightly newer) one from debian, they both work. That did the job for me, hope for you too! greets Lutz