If anyone could offer any help on this problem it would be appreciated. Ive got a g5 duel 1.8. It came with the stock 256 ram. I added two sticks of 512 from crucial and they were defiantly working. Then a week or two ago I looked at the about this mac to see that only the 256 was being recognised! I then swapped the 512 sticks into the ones occupied by the 128 bays, still not recognised. The machine will not start with only the 512 sticks in, and the 128 sticks work in all the slots. Confusing? So then I ran the hardware test, and it came back with a result of bad ram, whilst recognising that there are 2x 512 sticks in position. This looked like progress, so I called up crucial, and they were very helpful, and replaced them immediately. Yesterday I got the new ram put it in the g5 and same situation, no joy in any configuration. Before anyone says, the type of ram is correct! I dont believe that the 2nd batch of memory is at fault (if the 1st ever was!) so this leads me to blame the g5. What is happening, the 128 sticks do work in all of the slots (x4). The firmware of the computer is the most recent, - that has been the only change. Any suggestions would really be good, as Im not looking forward to the uk apple customer service, eg speaking to the far east call centre as Im sure anyone in the uk knows .