jMax is still under development, so you may sometimes experience problems that do not have a clear explanation, and you may not know what to do.
This page will list the solutions to commons problems as jMax evolve, collecting the experiences and workarounds collected along the way.
Under Ubuntu 9.10 32 and 64 bits, you may get this error, sometimes after a long freeze. Actually, it is not a jMax problem, but an alsa configuration problem. Alsa is trying to connect to a bluetooth audio device, but bluetooth is disabled.
The solution change depending if you want or not to use a bluetooth audio device. If you do not, you may just de-install the alsa bluetooth extension, with sudo apt-get purge bluez-alsa.
Otherwise, refer to Ubuntu/Alsa/Bluetooth configuration to activate bluetooth.
Most of the case, if you get a freeze and a NullPointerException it means that FTS, the computational engine, crashed, and that the user interface was not able to deal with the crash.
In normal condition you should get an error message of some kind, but there are a number of cases, for example during startup or shutdown, where the code is not robust enough.
You should see some improvements in this area later.