Strange lapto display issues

I have a really wierd problem with my laptop (Lenovo G550). Every so oftern my screen freezes and slowly fades out to white. I have tried googling and most people have been saying that it is the GPU overheating and you have to replace the thermal paste every couple of years. However if I give the display a sharp tap on the side it appears to spring back to life again. There was one person who had this problem and it turned out to be bad hard disk.

I am also getting BSODs relating to iastor.sys which is the Intel Matrix Storage controller. Again from googling people are recomending updating the driver but all these posts date back to 2006 and my laptop is only 2.5 years old.

So far I have tried cleaning out the inside of the laptop and the heatsinks and fans. I have also removed the Keyboard and looked at the display connectors and they do not appear to be damaged. I have tried running DFT to check the hard disk and that could not boot (it froze at "loading DFT...") I have copied off my profile information and plan to do a full chkdks and system wipe tonight but I am not convinced that it isn't a faulty display.

Any input would be appreciated.