nullPointerException - it's not what you think

I am a few days away from my practical exhibition for my Masters in Digital Art. The show is titled nullPointerException. Why am I posting this on my ubuntu blog? Because it was made in ubuntu using opensource software such as openframeworks and boodler. Because each work runs from a custom live USB disk running ubuntu. Because the concept is software related. The sensing devices are XBox Kinect and I am using the OpenNI and PrimeSense drivers to do the tracking I need.
 

Doing an technical installation in a gallery space poses some reliability problems. The pieces need to autoboot. If there is a power outage they need to startup again without intervention as the PCs are often hidden and out of reach. They need to run continuously for 3 weeks without intervention incase there isn't a power outage. In my case my budget didn't allow for 4 new pcs so I had to borrow what I could. This means boot from USB and don't touch the hard-drive. Initially I made lubuntu install disks but for the final set I customised a ubuntu oneiric desktop install image with UCK. Stripped out what I didn't need and installed kinect drivers and the artworks. It has the added advantage that I can give someone a flash disk and say "plug it into a pc, plug in the kinect, reboot and press F12, choose to boot from flash disk" and it works mostly depending on the pc the person chooses.