First, take a look at the error log and check if the messages it contains reveal the error. The general error log is located in /var/log/httpd/error_log or /var/log/apache2/error_log.

A proven approach is to track the log files in a console to see how the server reacts to an access. This can be done by entering tail -f /var/log/apache2/*_log in a root console.

Check the online bug database at http://bugs.apache.org/.

Read the relevant mailing lists and newsgroups. The mailing list for users is available at http://httpd.apache.org/userslist.html. Recommended newsgroups are comp.infosystems.www.servers.unix and related groups.

If none of these possibilities provide any solution and you are sure that you have detected a bug in Apache, report it at http://www.suse.de/feedback/.