Guest: Lubuntu 14.10 x64
Virtualbox: 4.3.20 (r96997)
CPU: AMD FX-8350 (not overclocked)
Now that I've installed Lubuntu 14.10, I cannot boot. This is what I get.

Since I was able to install Lubuntu, I figured I'd try enabling NPF again. This is what I get (some garbled view, with ultra low resolution).

If I disable NPF, and only allow 1 core, I can successfully boot...
Below was the old issue...
I'm not entirely sure what the improvement is with a nested page file, but I've had success in the past with it enabled. If NPF is enabled, I get these errors. A few times I also received a TCS calibration error.
With NPF off, I still receive all errors but it doesn't crash (like the fourth image).
Here's the fourth image, as I'm limited to 3 attachments.
