[Solved] Another Gigabyte P55-UD3R Memory problem

Problem: two memory slots showing as not enabled in BIOS.
I recently installed a P55-UD3R board with 4 2GB sticks of g.skill 1600 (PC3 12800) F3-12800CL8D-4GBRM. As I was only running XP32bit at the time didnt notice anything wrong until now installed Win7 64bit and expecting 8GB to show.

BIOS has been updated to F5 w/optimized settings and I've tried each memory stick by itself in slot 1 all ok.
With one in slot 1 and 2nd in slot 3 system shows only 2GB. If I add the other two sticks slots 3 and 4 show as not enabled giving me only 4GB.

I've searched various forums and really dont want to send the board or memory back so hoping there is a "magic" setting that fixes the issue. Thoughts?

The 2nd and 4th slots (from the CPU) are paired. Also the 1st and 3rd slots are paired. To run two sticks of RAM, put them in the second slot from the CPU and the furthest slot from the CPU (2nd and 4th physical slot). Enter BIOS and Load Optimized Defaults. Restart and verify that all 4GB are showing enabled. Make sure the RAM sticks are fully seated in the slots. One of the easiest things to do is not get them in all the way.

Once you get that working, put your next 2 sticks in the first and third (physical) slot. Load Optimized Defaults again and try again. 8 GBs can be tricky to get running. But it should recognize all sticks.

Update to last post - ekoostik - thanks a mill !!! Maybe not ideal but with a magnifying glass and steady hand managed to realign the pin, reseated the CPU and hey presto now have 8GB total memory