Yes, there is a connection, date-wise. I became a believer in the sixth century A.D. catastrophe theory last spring, after reading this thread in another forum ( http://forums.civfanatics.com/showthread.php?t=116880 ), and checking one of my textbooks to see what the Mayans were doing at that time. It said that no records of any events were kept at the city of Tikal between 534 and 593 A.D. Since 534 is close enough to the target date of 535 for whatever happened, be it a comet collision, volcanic eruption or whatever, that was the clincher for me.
I wasn't much impressed with David Keyes Book, 'Catastrophe.'
Stephen Oppenheimer has some excellent books too. He mentions in one of them that the Ice Age end may have been started by an impacting comet. Both of his books that I read are excellent.