Just purchased a new Gigabyte GA-MA78LMT-52 motherboard and a Gigabyte Superb 460W power supply and built a new computer. It operated well for about 3 days and then refused to start. Checked the switch and all connections but couldn't find anything wrong. The supplier then sent a test power supply and with this connected all worked well so sent the original PSU back to the supplier. I then get a message from the supplier saying on fault could be found with the PSU and it was returned to me. However, when again connected up it still refused to start. Where to from here?