Neverending sleep mode??

[pulse8]

My friend's computer went into sleep mode and never came out. She went to it, moved the mouse, hit the keyboard and nothing happened. She even tried hitting the reset button and nothing happened. Now the computer doesn't even POST. Question 1: What could cause this? Question 2: Does checked luggage x-ray machines affect computer hardware?

System Specs:
Soyo 5EH-M mobo
AMD K6-2 400
128MB PC100
STB Velocity 4400
SMC Ethernet Card

Thanks!
David