Why won't my PS3 play games?

I have a PS3 160 GB that I bought in July 2011 so it's a newer one and most games don't even show the disc on the menu screen to play. The disks however play on my friend's PS3 perfectly and they are newer games like MW3, Killzone 3, Skyrim, Black ops and a lot of other ones. Some games do play like GT5 but most of them don't even show a disc symbol, any reason why?

I have 83/160 GB storage left so it's not that I don't have enough memory.

Also, this just started happening, I played all these games before but just recently none of them have been able to play.

this happened to my old ps3... the reason was the laser was on its way out...i know that you can buy new laser units and repair it that way.

But before you do anything give sony a call, as you have only had it for a year or just over it should be still covered by the warrenty.