Nope, no problems here. Works as advertised. I've opened port 80 on our firewall and haven't had a issue. Sounds like something is messed up in your firewall.
What model firewall are you using? Have you looked at your firewall logs to see what ports SightMax is accessing?
What do you mean you "opened up port 80" on your firewall. You don't want everyone on the net to access your port 80 (as if you were running a webserver). You just need to access Sightmaxondemand port 80 - which should be able to happen without opening ports on your firewall.