A page fault that produces an error. Page fault errors can occur for any of the following reasons:

The virtual memory system becomes unstable due to a shortage of physical memory (RAM).
The virtual memory system becomes unstable due to a shortage of free disk space.
The virtual memory area is corrupted by a misbehaving application.
An application attempts to access data that is being modified by another running application.
The first two causes are the most common. These conditions can also cause a general protection fault (GPF).

An invalid page fault is also called a page fault error (PFE).