When you say "on a skype call," are you saying you have your webcam on when it happens? And what distribution are you running? I recommend using a program like cheese to see if it is your webcam that kernel panics your system, along with what the other two guys said and recheck your hardware. I would also take your computer fully apart, checking all connections and slots, and reseat everything just to be safe. As far as the RAM issue, I would run Memtest86 to check everything out.