Yanni
Your egrep output doesn't show the "Alias" line 1011 of httpd.conf. This is because my egrep was trying to be too clever and won't match "Alias" at the start of a line. The same would be true for "include" directives. Can you send what this shows:
grep -i "alias" /etc/httpd/conf/*.conf grep -i "include" /etc/httpd/conf/*.conf
Is there a reason why you're using "/opt/xymon" in your URL path instead of say "/xymon"? My Alias command looks like this:
Alias /xymon/ "/var/lib/xymon/www/"
I can't think why this would be a problem. Just a curiosity.
From what you have shown, it seems you have defined ScriptAlias twice: once in httpd.conf and once in xymon-apache.conf. You should remove all Xymon configuration from httpd.conf and instead let the settings in xymon-apache.conf be taken by Apache when it includes the file. You will have either "include *.conf" or "include xymon-apache.conf", and so you don't need to add anything into httpd.conf.
Cheers Jeremy