hello...
I registered just to tell my unfinished story with same problem
Few weeks ago, I got new i5 rig with 2x2GB of RAM on GA-P55-UD2 mb, but few days later I received some problems with graphics card which haven't been resolved since. So I returned it (first time) to store, and since I had 2 RAM modules and 4 DIMMs, I told them that I wanted them in dual channel ('cause they weren't in the first place). Two modules were in slots 1 and 2 instead of in slots 1 and 3 or 2 and 4. And I'm not allowed touching because of warranty.
So, week later, they said, ok, you can pick it up. I got home, turned on. 5 minutes later, same graphics problem appeared. And memory, they relocated one module from DIMM 2 to DIMM 4. Still no dual channel. But then I noticed in Win 7 only 2GBs are recognized. Went to BIOS, and same thing like here.
So, if they haven't replaced some other RAM modules, only location of one of them and this problem appeared, what am I supposed to think?
Rig is still 'being fixed' aldo due to lack of time, I haven't been able to annoy them about my problem. But day after tomorrow I will call them and be present when they 'check out'. So how can I (insist to) check is it mb, or RAM, or ?
I hope it is only the 'loosed hook' issue like in post above.