Maybe your default charset in the apache configuration is on UTF-8. As long as you don't need non-iso-8859-1 characters you can probably put that to iso-8859-1. Try if this solves the problem...
Change in the httpd.conf file (usually at /etc/httpd/conf) the line to
and check if it is okay now. You should restart apache after changing the entry.
By the way, if you have virtual hosts on your server this configuration could be overwritten by included configuration files. In this case you would have to check there too.