Troubleshooting possible RAM slot problem

i7, 5750, 3GB corsair, GA-ud3r-x58A, Bios F5.

After I installed windows, I noticed that of the 3GB of RAM I have installed, only 2 was usable. Using easytune 6, I OCed my pcu, But I could not get it to boot. SO started troubleshooting the RAM. First I took one stick out and booted up fine (after resetting to default bios settings) and I was able to OC just fine (cpu 3.2 and RAM 1600) So I thought I have a bad stick of RAM, So I took the stick that I had taken out and reinserted it in place of one of the known working sticks of RAM. I was able to boot and oc to the formentioned settings. Maybe I have a bad slot 5, but there is no way for me to test slot 5. The manual states that to run in dual channel with 2 sticks, slots 1 and 3 must be used and if I wanted to run a single stick only 1 or 3 can be used I'm using CM3X1G1600C8D which was listed as being compatible in 3 channel mode with my ud3r. Maybe there is a new bios version that I can try that will address this issue. Is there anything anyone can think of to help me get triple channel going?

Which OS are you running, including the architecture?

My fault

Darnit! Sorry for not including that.
Window 7 Pro 64.
I'm currently oced at 3.36MHz 2GB RAM at 1600MHz BCLK 160MHz In dual Channel.

Edit** Maybe this has somthing to do with it. The memory support list for my mobo has my memory on it: TR3X3G1600C8D (This is what I ordered and this is on the label of the mem sticks) Now when I open EasyTune6 the item# is CM3X1G1600C8D which is not on the memory support list.

Are you seeing the "2GB usable" next to Installed Memory (RAM): in Control Panel\System and Security\System?...

Installed Memory (RAM): 3GB (2GB usable)

http://www.overclockers.com/forums/showthread.php?p=6547159#post6547159

I have a bent pcu pin on my first and second mobo. How in the HELL did this happen? I'm sure Gigabyte would say that I did it, but twice. After fixing my first mobo, I was able to boot to windows and all 3GB of RAM is usable and I'm running triple channel. Now one would think just keep the first one and send the second one back since it still has issues. Well that pin that was bent on my first mobo looks funky. It wasn't so much bent, but it looks like it has been push down into it socket. I had to take my exacto knife and gently raise it up so that it would make contact with the cpu. I just don't know how long that will last. I'll begin trying to fix the second mobo and see if that will help.

EDIT** Now that I've looked at the pins on the second mobo, I have to say I'm mistaken; there are no pins bent. The difference is, the second mobo has a bios version of F5 (which is said to be the latest) and the first mobo has a version FA. I'll try and find the FA version and put it on the second mobo. I don't have a floppy disc though.

You can flash the BIOS using a USB thumb drive.