The ISP question was just a question. If you've already tried other places, great. That rules that out.
Regarding the other questions I had, like I mentioned above, I can't hit the page below:
http://www.voxpopuli.cc/vox/components/com_jfbconnect/assets/jfbcchannel.php
Can you look into what would be preventing that page from loading, as it's crucial to the operation of JFBConnect / Facebook communication.
I just tried to register on your site through Facebook, and got a 500 Internal Server Error at:
http://www.voxpopuli.cc/vox/index.php?/component/option,com_jfbconnect/view,loginregister/
This is probably related to the above jfbcchannel file not being loaded, but can you tell me what SEF extension you're using? If you can, please go into it's configuration area and have it 'skip' URLs for JFBConnect. If you're not sure how to do this, once we know what extension you're using, we can probably give suggestions.
Finally, for the 500 error, that's usually a sign of a PHP error on the page (can be many other things though). Once you get the jfbcchannel file above working, and SEF disabled, if you're still getting the error, can you turn off GZip compression (if enabled) and turn error reporting to maximum in the Global configuration area? That should print out a error of what's happening, if it's a PHP problem, that will help us narrow things down.
Thanks,
Alex