Arrays do not render vertical lines or horizontal lines correctly

[Rowan Richards]

When making an array, for example:

"\begin{array}{|c|c|c|} a & b & c \\ d & e & f \\ \end{array}"
only the outer two vertical lines will render
Further,
if a horizontal line is placed on top:

"\begin{array}{|c|c|c|} \hline a & b & c \\ d & e & f \\ \end{array}"
the top line renders fine.

when another is added anywhere else:
"\begin{array}{|c|c|c|} \hline a & b & c \\ d & e & f \\ \hline \end{array}"

the whole section becomes a black box.

Further, any lines placed between rows are not rendered.