Ahhh....
Assuming that your listing of "iptables -L" reveals no offending local firewalls, I'm inclined to believe that your SSL certificate does not support the IP address as the named certified site.
I'm a bit rusty on this, but I believe that SSL certificates can only validate the site for a hostname? So if you are accessing the site by IP address, it's likely that your error_log from Apache is actually showing an access attempt that cannot be resolved.
Try this:
On one client machine (preferably non-Win) create an entry in the 'hosts' file to map some nonsense name (or your cert hostname) to the real IP. Then, using the client's browser, try to reach the site by name.
All of this assumes that your certificate is valid, that mod_ssl is being loaded and running correctly, that httpd.conf is properly configured to listen on the proper IP, that your internal routing tables are correct, that there is not another machine competing for the same IP as your server,.... etc.
Good luck!
D.E.R. Management - IT Project Management Consulting