Hi Jim, although I'm not near any of my tools at this time... I seem to recall that most blades come with a "maximum RPM" printed on the blade. Check this out and also the RPM's of the table saw (owner's manual will list this), and if the saw provides more RPM's than the blade is listed for, well there's the answer.
Above all else, do as Dodgeman said... quit using the blades until you know what is EXACTLY happening! I've never had it happen, but everytime I turn on my tablesaw, a blade shooting off is always in the back of my mind.