My son reminds me that a couple of months ago, we had a similar scare. When we investigated it appeared that the power supply unit (which is external on our Jap PS2) - the glue had melted that holds the box together. We left well alone as it was extewrnal to the PS2. It may well be that you play with your PAL PS2 horizontal and the glue in the internal PSU (it is internal isn't it?) has also melted. Do open up and have a look.