XPS 720 Memory Parity error

I put my desktop to sleep last night. When I woke up the PC I got the following blue screen

*** HARDWARE MALFUNCTION

Call your hardware vendor for support

NMI: Parity Check / memory parity Error

*** The system has halted ***

So I powered the PC off, than back on, the PC got to the Windows initial boot-up screen (without any motherboard warning "beeps") than the memory error screen shows up again.

My first thought (of course) is that one of the memory modules (sticks) is bad.

Trouble shooting
1) Removed and re-seated all four memory sticks (modules) in the same slots. No good.
2) Moved the sticks to different slots. No good.
3) Tried just two of the memory sticks at a time. No good.
4) Checked Bios and I could not find any memory issues there.
5) Removed and re-seated network card, video card, and sound. No good.

In the past I have had issues with the memory, however those issues were corrected after I pulled and re-seated the memory. With regards to those errors I did get the motherboard warning "beeps".

Questions
1) If the memory was bad wouldn't the Bios indicate an issue?
2) If the memory was bad would it still be able to boot-up to the Windows screen?

Any assistance would be appreciated.