A couple of months back I smelt a uriny smell in my computer room, pretty sure it wasn't me. Went on for 4 or 5 days then one night my 4 gang extension plug in the wall socket decided to melt itself to the wall socket with the most horrendous cracking noise. Took the plug apart, after it had cooled down, and it looked like the neutral wire had shorted to the earth wire. According to DIY.not forums its likely to have been a slack connection on the neutral pin which lead to a high resistance joint. Over the years it must have overheated to the point the insulation broke down and caused the short. Damn lucky I was in the room when it happened. But yeah, I put the smell down to the final stages of the insulation melting/weeping before the big bang.