Hmm, ok, I was seeing the exact same rebooting issue. Didn't realize it was an initialization issue on powerup. Just curious, what drivers/programs are you using to control it on ubuntu?
I'm using a combination of boblight, ruby-usb and combustd to get it to work. This isn't my blog but I used this as a guideline to get everything up and running:
http://slickeel.wordpress.com/2011/03/25/philips-ambx-starte...
The tricky thing was realizing I had to have it "initialize" in Windows before this would work.