In R2013a, a curious glitch has emerged in the behavior of the documentation. When I type 'doc', go to the home page, and click on 'Supplemental Software', I get the documentation for this package (and some others). However, the display flickers. MATLAB Support uncovered the source of the problem: the line
<meta http-equiv="REFRESH" content="0;url=xunit_product_page.html">
in the file index.html.
The fix was to delete index.html and replace it with a copy of xunit_product_page.html, renamed to index.html.