Only half of RAM detected on MSI P55-GD65

[Rich Braun]

Early last month I bought my first Core i-series system, build out of a Core
i5-760 CPU, an MSI P55-GD65 motherboard, and two DDR3 4GB RAM modules.  When I
first built it I noticed two oddities:

1) In dual-channel RAM config (sockets 1/3 populated), it only recognized 4GB
out of the 8GB of RAM
2) It would power-cycle about 3-4 times before coming up.

At the time, I opted to run single-channel RAM (sockets 1/2) and not worry
about the power-cycling weirdness.

Last week I bought two more RAM modules and the system didn't recognize any
additional RAM.

Today I spent about 2 hours digging into this and came up completely empty: 
Googling for answers leads me to believe I should scrap the mainboard and
start over with something else that doesn't contain a Foxconn CPU socket.

An update to the newest BIOS release (1.10) does fix the bizarre power-cycling
issue.  But the RAM issue remains.  (BIOS splash-screen and other menus report
all the RAM I installed, but Linux uses only half the available amount,
whether I install 2 modules or 4; there is a lot of chatter online about
"reserved memory", a BIOS feature called "memory remapping" which is not
selectable in the MSI BIOS, bent CPU socket pins, and on and on...)

What would y'all do about this?  Take the whole thing into Microcenter and say
"debug this"?  (Hah.)  Or just toss the mainboard into the basement parts bin
and start over, like I'm now inclined to do?

-rich