Inspiron N5050 random letters and shutdown/won't power up

Posting this mostly in case anyone else has the issue. Also hoping Dell might know why this is happening.

I bought a N5050 for my friend about a year ago, and a few months back she told me her computer was possessed - weird keypresses and randomly shutting off. I came over and before I even powered up the computer cleaned the keyboard - popped it out, reseated it, removed kid crumbs, etc. Then everything was fine.

last week she said she had the same problem. told her to buy some canned air. She said it got better then her computer stopped booting entirely. I came over, checked stuff out.

Before I did anything, no lights on laptop front would turn on. if I held the power button down or pressed it repeatedly the cd light would come on briefly, sometimes (rarely), but not even long enough for me to hit eject.

I popped out the keyboard, and cleaned it, then while the keyboard was still out, but connected w/ the ribbon, I powered it up w/ keyboard just resting on the laptop. it powered up just fine, and I saw all the lights were on. Put the keyboard in, and it powered off. took keyboard out again, powered it up, then touched the tabs on the keyboard to the metal above the HD and other stuff and saw that it typed random characters. Weird. So I put electrical tape on the bottom of the tabs (where there isn't a clear plastic coating) and put the keyboard in - now the computer works fine.

So I don't understand... why did it work ok for almost a year before this problem developed? It looks like the tabs are designed to touch the metal parts below them, so I am wondering if some grounding somewhere else came loose and caused this problem. 

Regardless though, the four tiny pcs of electrical tape made all the bad things go away and the computer works again.. anybody have any idea why?