New RAM Mysterious Problem: HELP!

[vslo]

Ok, I gave up after those 3 hours of testing. Here's whats happening:
I bought 2 of this (Kingston 2GB 1333MHz DDR3 Non-ECC CL9 SODIMM, Standard 256M X 64 Non-ECC 1333MHz 204-pin Unbuffered) to upgrade my iMac i3 late mid 2010.
Infos: -I have Lion installed
-I don't use any kind of external hard drive
-I have nothing but the power cord connected
After installing, everything was beautiful. Lion running smooth. The system was 100% better with the 8gb.
I tried to print a document ( I have a Wireless HP Photosmart D110A if that matters ) and the iMac suddenly frozen and started to make those 3 beeps that indicates RAM problem. I booted and in the same printing process it frozen again, with the beeps. Then, I took off 1 of the modules, and I wasn't able to reproduce the problem. Opened a lot of apps, used a lot of ram, printed the document, everything.
I was SURE that I got a bad module, but decided to try with the other one. For my surprise, I couldn't reproduce the freeze ! Then again I tried with the 8gb, and while booting, it frozen and beeped. I Changed the modules positions and the problem remained.
Then I took off all the RAM and tried 1 by 1 (only 2gb) all the 4 modules. And couldn't reproduce it.
I tested all modules with Rember and the Apple Hardware Test. All ok.

So, what is going on? My iMac can't handle 8gb ? I can't think of anything !
HEEEELP ME!!! I have seven days to change my new RAM.
Should I take it to the Apple Care?

EDIT:
Running on 6gb apparently makes it stable, no matter what combination of modules I use. With Prime95 I can easily reproduce the problem using 8gb. With 6gb, everything is fine. Might be my logic board failing to recognize 8gb ?

 

[Detrius]

Maybe you have a bad RAM slot and you just happen to leave the same RAM slot empty whenever you have three modules installed.

 

[macking104]

Have you called Kingston: Kingston Technical Support in the United States and Canada can be contacted directly by calling: +1 (714) 435-2639 or toll-free at: +1 (800) 435-0640.

Or Apple?

 

[vslo]

Maybe you have a bad RAM slot and you just happen to leave the same RAM slot empty whenever you have three modules installed.

Nop, I tried with all the slots. Right now my stock ram is running on the other 2 slots that were empty. I think its a problem with the iMac handling 8gb. I think it makes the i3 run unstable, as it is DDR3 and it should run as triple channel.
Or its a compatibility problem with the ram.
Right now I am running it stable with the 6GB. I can't change one of the modules since I don't know which would be the bad one, if there is a bad one.
If the problem is in the slot, I can't figured out which one is either, since both passed the tests...
Well, I've seen some people with the same problem in apple forums, but they couldn't figure out whats going on. Some got Logic Board changes, even iMac changed and the problem persisted.