Q: Macbook Pro Ram Upgrading Problems

I have a bit of an issue that I am completely dumbfounded over..

I just bought some new RAM to upgrade my old macbook..

I have the 15-inch, 2.53GHz, Mid 2009 model MacBook Pro

Per Apple Support Website  MacBook Pro: How to remove or install memory - Apple Support

PC3-12800 sticks are compatible, I purchased 2 4gb Sticks to meet its maximum size allowed, 8gb

I pull out the old ram, to my surprise it is PC3-8500

I put both in, I get the 3 beeps of death.... Oh crap

Re-seat both sticks, make sure they are both in there snug, No-Go still the 3 beeps...

I put 1 in at a time, bottom slot.. No-GO

I try the Top Slot, 1 at a time.. No-Go

Thinking I bought bad ram sticks, I put the old back in.. Now 1 beep.. What the heck!

I clean all contacts, on the board and on all 4 sticks of ram.. Put the old in, She boots right up.

Just to play around I put in 1 stick of the old and 1 new in, surprisingly it boots right up!!

I quickly turn it off, take out the old to have the new in only, and still 3 beeps...

Put the old in again so its 1 old 1 new, and boots up, Now is registering 6 gigs...

2Gb in one, 4 Gb in the other... Now how the heck is this possible ?

The RAM is working or it wouldn't register at all, so why isn't both new sticks working with each-other ? hmmm Any ideas ?