What do you think could be the biggest threats to an advanced, high-tech civilization?

[Caligula F. Onion]

Suppose that Human civilization reaches an advanced, high-tech phase kind of like in science fiction. How would the threats to civilization and Humanity change at that time? Would a lot of the same modern threats like nuclear weapons, overpopulation, and environmental disaster be at least as much of a problem then as they are now? Which threats might be handled better? What would be the biggest new threats?

What factor is the most likely one to cause the collapse of an advanced, high-tech civilization?