Wikimedia Bugzilla is closed!

When I try to render something like:
\begin{matrix} x & y \\ z & v \end{matrix}

texvc returns something like:
+b99890966e1b997497211428f8e3419d-

however, there is no such file b99890966e1b997497211428f8e3419d.png in the
output directory.  

It appears that all expressions that use \begin{} do not work.  All other
expressions appear to render fine.

sample invocation:

achin@localhost:~public_html$ ./texvc /tmp ./texvc_output/ "\\begin{matrix}
\\frac{2}{4} \\end{matrix}"
+fecac241ae56c2763754a23d0fa4e4b4-
achin@localhost:~public_html$