Does the circuit board use one of the through holes of the socketed chip to make a transistion from the bottom to the top of the board for a power /gnd carrying pcb trace, maybe a power through hole is damaged/intermittent or maybe the extra loading offered by the sram on the supply is just enough to make a faulty diode or other component work properly nearby. It doesn't really make any sense that it works just by having a chip in the socket with its data and addressing lines floating even.