What is Damaging my Motherboard??

My motherboard, on my Lenovo 510s has been replaced again, 3 months after replacing it. I suddenly started getting random restarts, sometimes with colored stripes.
As I see it, my laptop has 3 issues that may have caused the problem, and I'd like to know which is probably responsible for my motherboard dying 3 months after replacement:
1. Headphone jack supplying noisy output while using the official audio drivers. Problem gone when using Windows' own audio driver. First colored stripes and restart appeared when using the headphones, with Windows' audio driver.
2. Could it be a faulty ram card? If so, will a memtest confirm it?
3. I have a very small tear on my power supply cord (maybe 1.5 mm).

Which is most likely to have ruined a new motherboard after less than 3 months, or was it just a bad installation by the technician? The laptop is only 14 months old and I don't want to part from it just yet. The one year warranty has passed, but I still got about 3 months warranty on the motherboard if it fails again, which I'm really really trying to avoid.

Thanks so much and all the best,

Muli

ThrashZone said:

Hi,
Probably a defective unit
You don't say the region where you live u.s.a. ..... so power grid could be a issue = lighting strikes.....
Do you use a surge protector ?

Thanks! I live in Europe. What defective unit? Motherboard / ram / audio card/ power supply?