PS2 V9 Freezing, then black screen

I have a V9 PS2 here, Messiah2 1.33b installed. PS2 works for a while, 1 - 10 mins. Then suddenly the game freezes, usually during loading levels etc. The PS2 cant be reset or disk ejected unless its switched off at the back. When the PS2 is turned back on, all i get is a black screen. eject works etc, but nothing is happening on screen.
If I wait ten minutes or so, the machine starts normally again, and same freezing occurs,

Any ideas peeps? Could there be a solder bridge somwhere?
Would a Thicker ground help?

OK,
I changed the ground cable and all seems good. I didnt know Messiah2 suffered from ground bounce?