I have been using nagios for quite a while, and this is teh first time I have had this problem. The web interface has been working wonderfully well, but all of a sudden, the system was unable to display the host and service data, The error that is seen is this one:
Error: Could not read host and service status information!
nagios is running, there are no errors in the logs, no permissions or ownerships have changed on the system. I can't think of anything that has changed on the system at all. The cgi directory is ownded by nagios:nagios, and apache is in the nagios group. The permissions on the cgi files and the cgi directory are 775. The log files are similarly all owned by nagios:nagios with read/execute permission for everyone.
There are no errors in the httpd log file either, and ther have been no changes to the webserver.