Most likely faulty hardware, may even be the motherboard that's developed a fault. You'll have to let a laptop repair technician take a look at it as it's impossible to diagnose that kind of problem without someone opening it up who knows how to test it and has the knowledge and tools required.
My laptop is also sony seri e, and I have exactly the same problem with yours. As I noticed, you had this problem one year ago, and you have hopefully fixed it up to now. Could you please let me know what the problem was, and how did you fix it?