Were these bought specific for this board? The Micron part number is not on the QVL from Asus. What is the Crucial CTxxxxxxx number for these sticks? Can be they are simply not compatible with this board, if they were bought from Crucial for this board, send them a message stating your troubles and ask for an RMA, they should send you a replacement set. Oh and ofcourse you already replaced your CMOS battery with a fresh new one + checked for bad capacitors on the board (see http://www.badcaps.net
for info), right?
Sorry, but you just asked for the long gory details!
I was hoping to spare folks from paths that I had already closed but here goes. The system has worked very reliably for quite a few years with 2 sets of memory. The original set was 2-512Mb double sided Crucial CT6464Z40B.M16FKY. Around 2008 I added 2-1Gb Corsair ValuSelect VS1GB400C3 sticks. Everyone was happy until several months ago when the system developed a noisy video problem.
The video problem was repaired with a new adapter card. While doing the repair I noticed the start of bulging caps on the MB. I also noticed more bulging caps in the output section of the Antec Truepower 430 PSU. I replaced the MB caps with Nichicon HZ series. I kept the old PSU while researching a new one. The system ran reliably for several more months AFTER replacing the MB caps AND AFTER replacing the video adapter..
For the new PSU I decided on a Corsair by Seasonic TX650 V2. This is a well reviewed quality supply. The recent set of problems began immediately upon installing this new PSU. However I don't believe that this is a PSU issue. The output voltages measure near perfect with a good digital meter as well as SpeedFan. I even went as far as looking at the loaded output voltages on an oscilloscope and they all met the ATX power supply specification. The connection between the current symptoms and the PSU is still unclear. My speculation is that the new PSU being much less noisy and having slightly different DC voltages has affected the memory operating voltage on the MB for the worse.
So back to the Crucial memory. Since it was the original set and a process generation or 2 behind the Corsair it was naturally slower than the newer Corsair sticks. The Crucial memory exhibited much worse symptoms than the newer Corsair. I have already RMA'd this memory and Crucial has sent the latest (current generation) single sided (2X density + unknown die shrinks) as the replacement. It's part number is CT6464Z40B.8TFY.
So now I have 2 sets of RAM that exhibit approximately the same symptoms. I am currently only running one set at a time. The only potential problem that I currently see is that the memory timing as set by the BIOS is faster than the SPD specification of the memory and that the BIOS is so far refusing to allow me to change it. I will agree to a memory problem ONLY when the memory timings match the SPD values and the POST still doesn't execute properly.
BTW, The CMOS battery has been changed and reads 3.07 volts after the system has been unplugged for 24 hours. While plugged in the CMOS is maintained by the +5VSB supply from the PSU so this is really a moot point . Also the Asus QVL for memory has not been maintained. As I recall the original Crucial parts were on the QVL.
Thanks for your indulgence!