Optus "do" shape bandwidth if you overstep their monthly bandwidth usage (ie: have maximum download/upload limit per month). Most ISP's in OZ do shape. Especially for dsl2 usage. What is your speed plan?

Try a speed test: Choose nearest location for a speed test & only have your browser open: http://www.t1shopper.com/tools/speedtest/

Try enabling UPnP on your device to stop the firewall problem.
Open a web browser like internet explorer or Netscape. Enter the ip address of your router in the address bar of your browser. By default the ip address should be set to 192.168.1.1
http://192.168.1.1

You should see a box prompting you for your username and password. Enter your username and password now. By default the username is blank, and the password is admin. Click the Ok button to log in to your router.

Now search the tabs & look for UPnP. If you find it, enable it & save settings.