RAM disappeared/reappeared?

[roleki]

About two months ago, I built a CAD machine around an ASUS P6T Deluxe V2 and a Corsair 6GB triple-channel kit; the documentation for the mainboard specifically qualifies that particular RAM kit to be acceptable in either 2-DIMM, 3-DIMM, 4-DIMM, or 6-DIMM configurations. I did what I felt was an appropriate 'burn-in' (24 hours of prime95) and turned it over to the end-user so he could start designing stuff with it.

Everything worked fine, but he started getting out-of-memory errors (no hardware problem at this point, just the SolidWorks drawing he's working with being ridiculously outsized) so I ordered an identical 6GB triple channel kit and installed it in-place; I DID NOT do a burn-in of this configuration, but nonetheless it was working without a hitch for two weeks...

Then this morning he reported his machine was acting really sluggish. Check of Task Manager shows only 8GB of RAM installed. We reboot it, and there's 12GB again. I re-seated the RAM and haven't been able to replicate the problem, but with only a couple weeks left for me to be able to return it, I thought maybe I should check around and see if anyone else has experienced this problem & maybe has an idea of what may have happened here.

So... any ideas?

 

[EXT64]

Well, I have had ram "disappear" in a computer at work. A simple reseat of the ram fixed that.

The other possibility for 1156/1366 is a bent pin in the CPU "socket". Normally if that is the case the RAM is permanently gone, so that might not be the case this time.