Newbie needs help with file uploads

I am having difficulty with supporting file uploads from remote domains. I currently am able to upload files if I am on my local area network to the apache server but when I try from another network, the brower times out and comes back with a cannot find server. I suspect either my apache/php configuration is wrong ( I looked at the php_safe directives in the php.ini file but could not see a problem there) or I have a problem with my firewall. I have port 80 open and can submit forms and the like but cannot seem to upload files. I am currently using apache 1.3.20 and php 4.0.6. Help anyone...