Hello, I was trying to upgrade from 4GB RAM to 8GB in my wife's computer and am getting an odd problem. I got 2 x 4GB sticks to put in, but the computer freezes on startup when they are both installed. It also freezes on start up if I install 1 on the new sticks and leave the other port free (tried both sticks). Here is the part that is confusing me, if I use 1 of the old sticks and 1 of the new sticks (for a total of 6GB) everything works fine. I was thinking that the computer was running on just the old 2GB stick, and not picking up on the new 4GB stick but when I looked at the 'about this Mac' screen it says 6GB, and says both are working fine. The computer is also running faster, so it seems like the new stick is working. I also tried the 6GB setup with both the new sticks to see if either was defective, but they both seem to work fine (as long as they are not used together). I was hoping that someone could help me understand what is going on here. Thank you P.S. Please let me know if this is the wrong place for the post and I will re-post in the proper place.