"Cold boot" memory errors - Please help

OK, that title is not very descriptive, but I don't know any other way to describe it.
First here is the system:

chip: Intel core i5 750
mb: Asus P7P55D running the latest firmware
ram: OCZ3P1600LV4GK (pc 1600 7-7-7-20, though I am running it completely stock so it is running at a much slower speed)
Vid: Nvidia geforce 6800GT (made by MSI, this is really old, but this rig is not for gaming)
Power Supply: Enermax ELT620AWT
OS: not relevant, I am booting into memtest86+ to demonstrate the problem
other: Hard Drives and a CD rom

The problem:
1) If turn off my computer for several hours (say overnight) and I turn it on
2) boot directly into memtest86+: There will be millions of memory errors
3) hit the 'reset' button on my computer or hit ctrl+alt+del or hit esc (reboots in memtest)
4) boot back into memtest again millions of memory errors
5) and this is the weird part, Power off (hold the power button for a few seconds) and power back on
6) boot into memtest86+: CLEAN BILL OF HEALTH (no memory errors)

At this point, I have RMAd the RAM 3 times (they upgraded me from gold to platinum), my mother board once, and my CPU once.
Note that if instead of booting into memtest i boot into an operating system, it will crash, until I do the shutdown and restart. I am not quite sure how long my computer must be off to make this problem happen.

Even when my system boots it is unstable (sometimes it is fine, but sometimes it hangs. Sometimes memtest will run for a day with no errors, sometimes an error will show up).


Anyone have any ideas? I have RMAd all the new components int the machine, and I am still having the issue. I have tried this with 1 stick of ram (with each module), same problem. I have tried this with completely default settings on my mobo, same problem. This is fairly frustrating to test, because I can only run a test after a long cool down period. This has been going on for several months since I first built the system.

Thanks!
w0den