Error: Could not read host and service status information!
The most common cause of this error message (especially for new users), is the fact that Nagios is not actually running. If Nagios is indeed not running, this is a normal error message. It simply indicates that the CGIs could not obtain the current status of hosts and services that are being monitored. If you've just installed things, make sure you read the documentation on starting Nagios.
Some other things you should check in order to resolve this error include:
Make sure you read the documentation on installing, configuring and running Nagios thoroughly before continuing. If all else fails, try sending a message to one of the mailing lists. More information can be found at http://www.nagios.org.