Hi, I just upgraded my memory on my G4 Powermac 1.25 Duallie (MDD). I'm not very technical so i went and bought a stick of: PC 2700 / 512 mb / 333 Mhz / DDR ram (Kingston brand, Samsung chips) I have 4 slots (don't need pairing), 2 with 256 mbps, one with 512 mbps, one free (hence my decision to fill it). Now it froze my system. I called in Kingston memory and they said "you have model KVR333/512R memory, it should work but we have KTA-G4333/512 especially for macs". Try going to your retailer to get a different KVR333/512R because it may be bad memory or you just may be out of luck... He said it "should" work but ... I hate the word should. Now have any of you had this issue? My retailer (tiger direct) doesn't do returns on memory, they want me to bring in the system and the memory to test it out. Is the model of memory different? Any thoughts on your end I am not a technical person and didn't realize that after I got all the specs right that there was a special model number. Thanks for your help.