Well, after the update it failed to appear in the plugin list. At the top of the plugin page was a warning that 3 plugins had been uninstalled because they caused an error. When I tried to install the uninstalled plugins, they could not be installed automatically.
I visited the site via FTP and had to manually delete google site map plugin and the others which had caused the errors.
I was then able to revert back to a prior stable version of google site maps and was able to reinstall the other plugins.
I do not know how or why this happened but it happened when I "upgraded" google site maps plugin.