Its very strange that there would be no compression on all cylinders. Are you certain that your gauge is working? Try putting your finger into each spark plug hole and crank it over. If there is any compression at all it will blow past your finger.....was it running and quit or just wont start. We will need some more information.....
What you describe is a very unusual situation but has been noted before. The most common and worse case scenario is failed timing belts. If one fails it can run in to the other and cause both to fail. then all 6 cylinders loose compression.
With that said there has been a few times that these bikes , for whatever reason, have issues with valve adjusters. The adjusters pump up so much they hold the valves open. I think some havve had success eliminating this issue by taking out the spark plugs. On the centerstand and in high gear slowly turn the wheel backwards so the oil trapped in the adjusters can relieve itself. Though several have had this issue no one has talked of a possible cause. Do you run a real heavy oil?
Check these two things and keep us informed.
If it was running fine one minute, and lost compression it does sound like cam belt failure. Try taking the cam belt covers off and checking those. Are cam belts original, or just recently changed?
Keep us posted as to what you find out.