Can i use from behind a firewall, through a proxy?

In our local home network, we have have several kids’ computers which are firewalled from the internet. This is so that they must access the internet by pointing their proxy settings at an IP address for a proxy machine on our network (we use Web Safety by diladele, and we love it. This is a great proxy filter that protects kids from tons of garbage on the web).

These computers are able to access internet just fine. However, I keep getting connection errors when I try to create or join a meeting at Even if I set the proxy to ignore traffic going to, when I try to launch or join a meeting at, the webpage says “disconnected from server”.

Is is possible to connect to through a local proxy? Is my problem likely the proxy or my local firewall?