internet proxy

The ISP has the site filters on for a reason, so in bypassing them, you might be invalidating your contract with them.
To do so might make them terminate your contract, leaving you without an ISP.
I want to make sure you know this.

Now, that said, try this trick. See if you can route your traffic through ANOTHER proxy server. Go here:
http://www.publicproxyservers.com/index.html
to get a list of open public proxy servers. Fill in your proxy info in Internet Explorer with one of the public proxy servers listed on the site.
This might work. I've done this before to bypass proxy servers.
But remember, it is against the policy of your ISP to do this, from the sounds.