I had purchased all 8 GB, and it was a model that came with 1.5 GB onboard, although that was all that the system could detect. In reality, it had four 512 MB sticks inside.My order should be here soon I hope I dont have the issue you had. Was the G5 like mine, same specs? Were you upgrading from 4GB to 8? Did you purchase all new 8GB or added to?
Curiously enough, I did try to mix and match two of these sticks into the system when it became clear that I wouldn't be able to max out all 8 GB of my RAM. I thought it would be fine to settle with just 7 GB, but that didn't pan out, so now I'm only using 6 GB.