Got spare memory? if so, exchange it and re-test.
Or remove single modules and re-test.

While computer is open check for dust.  Especially on the memory chips or around the memory sockets.  Remove chips and wipe clean with soft tissue paper.  Blow out memory sockets and reinsert chips.

Also check motherboard for distorted capacitors but if only six months old I wouldn't expect that.

Also if it is six months old and the problem still occurs use the warranty.

since it's only a couple of months old, you have a warranty
return it, and have it repaired
do not swap parts - you risk voiding warranty !

If it's self built, and the fault occurs frequently, try running it with only half the memory installed.  Then, repeat with the other half.

Thanks all!  It's cyberpower PC.... it's under warranty but I have to ship it back and be without it probably a week at least... I work from home, so I need it every day... I asked them if I could pay a deposit and get a loaner, swap out the hard drive, send them my unit to test, etc.... not an option...

It's only a couple months old, so not much dust in there yet, and it's location allows tons of air flow (the machine it self is very well ventilated.

I'm not overclocking and I'm not stressing it much either... plenty of office multitasking, but I'm not running games on it or anything...

Ill try memtest again and see what happens...

could be there are shorts : " It makes a wierd noise through speakers"
or a device is gone bad
are there any errors in device manager?

check also event viewer for errors

Thanks! No errors in device manager - I will check event log after the next occurrence...

you can test it by booting from a live cd, like Knoppix :
http://www.knopper.net/knoppix-mirrors/index-en.html

thanks all - sorry been busy - will try to get in some more memtest this weekend and report back

no problem

obligatory bump so EE will let me post a different question...  When I have time I will troubleshoot this more and report results

Heat was the issue it seems.... just above the memory I installed two fans and have not had any issues since.

I want to award the points to those who mentioned heat.  A new fan fixed my issue

a pc of a couple of months should not crash by heat
i would have it repaired under warranty - or replaced !

I had replaced the ram - it had 2x4GB sticks of ram and I put in 2x8GB sticks that had heatsinks on the ram which reduced the air space between the two sticks....  not sure the overheat ever happened with the original 2x4GB sticks so not sure I can blame manufacturer.... anyway... the ram had a vent and place for a fan just above it, so now air is better actively drawn across and between the ram sticks.

it can also be the cpu which is overheating
install speedfan to monitor temps ( you can temporarily disconnect the fan to check what is heating up)
http://www.almico.com/speedfan.php

thanks!  If I have problems again i will check that out.  But as long as it's running good, that's all I care about :-)

-i don't agree - if you have a problem that is not corrected - it will bite you later

Im confused.... what problem might I have?  (honestly asking :-) I am naive... )....   I would figure if I am having some overheating I need a fan, I have fans, if that solves my overheating, I dont have a problem.... are you saying that there is an overheating problem that is solved at a higher level than just adding fans?

>>   what problem might I have?    <<   what was your question here about?  did you forget that?
you installed a fan so it's a bit better cooled - but that is not normal
best look into it, and if needed, take proper action - maybe change the heatsink of a chip, or the heatpaste

**note that it can also befailing hardware - just starting

I don't want to seem like I am questioning you in any sort of rude way.  I'm sure you know what you're talking about a lot more than I do :-)

That said - I'm still a little bit confused.  If the system was designed for a particular build and then I modify the build, it's not normal to sometimes have to install more fans?  I thought that was pretty standard and often overlooked.  I doubled the memory and the heatsinks on the memory leave 25-50% the amount of space between chips.  Mere milimeters....  That creates more heat.  

It might also be worth mentioning that the mobo is at the top back of the case.  CPU and RAM are just below two spots for 120mm fans, but no fans were there.   But big holes so heat would probably normally naturally rise quite well.... I have this mounted under a desk though so there is only about 2-3 inches between top of PC underside of desk.... so that might also be effecting how well heat escaped without active fans there.  

With all that in mind you think I really need to do the additional troubleshooting?   Crazy busy, so trying to avoid anything I don't "need" to do.... taking PC out of desk mount and opening it, etc plugging it all back up just to unplug fans and run a thing and then do it all again, is more work than if I just had the PC setting on top of a desk :-)

>>  the heatsinks on the memory leave 25-50% the amount of space between chips  <<  then why install heatsinks, if theyincrease the heat?  not logical - the temperatures should be lower and NOT need addidional cooling

>>  you think I really need to do the additional troubleshooting?   <<  yes

is the case a normal case?  with a power supply with fan?
post mobo and case  model  for more info