Some PC hardware won't work for no obvious reason at all, although it works sometimes and stops suddenly.
[HINT]
Try using a hair dryer to heat-up the affected piece of hardware (be careful, since you might overheat some component) and see if it works then.
I've once had a network adapter which disfunctioned if my room-temperature was below 25°C, so I had to warm it up a bit using a hair dryer - I did this WHILE the system was running
Worked quite well, but I decided pretty soon to buy a new one, since my whole motherboard got quite hot during the process.