I've seen the ram go bad on the G5 series -- other issues -- you have to used paired memory. Though word of advice -- you don't have to use "mac specific" memory -- all you have to do is match the ddr type and speed. The CD's that came with the G5 should have a memory test util on them (tech tool pro / lite) may be worth running it. Also if the tower has the original maxtor sata hard drive in it, scrap it -- I've had a bunch overheat on me, they were a junky drive. If the memory does test bad, its worth to replace all of it, I would recommend going with memory that has heatsinks on it -- patriot, gskill are both great brands.