Okay, some investigation has shown that the virtualhost entries for webmail.* were removed from the httpd.include file. More than that, though, Horde itself appears to have been deleted. /home/httpd/vhosts/webmail no longer exists. What gives?
Okay, final resolution... it uninstalled Horde without reinstalling the new version. a 'yum install psa-horde psa-imp etc.' worked. Irritating, but not critical
