There is an issue that prevents Praat from running on Ubuntu 11.10, this can be solved if one runs Praat while suspending PulseAudio. This is done from the Terminal (use sudo in case that the following does not work).
pasuspender — praat
This should run Praat without problems (at 44.1 kHz, or at any sample rate from version 5.3.04 on).
(see also the discussion in Praat Users Group).