So you are unable to view a website that has heavy java?
I don't know much about java but I can't see any network equipment causing java problems. Are you sure it isn't something to do with the machines on your network? Can you see the website w/o problems from a different location/internet connection on a machine that can't see it on your network?
Hm... You could check and see if your firewall is blocking content fairly easily I think. If you put a linux proxy server in a dmz/give it an external ip you should be able to bypass any sort of filtering the firewall is doing. If you arn't very versed in linux any of the free router distros should let you set up a proxy fairly quickly and easily. Just find a spare machine, put 2 nics in it, install a linux router distro (i like clarkconnect and ipcop), put it in a dmz/give it external ip and point your browser to it.