Solved.
Sorry for the delay in getting back with a result but I wanted to make sure it had worked before posting.
I ended up contacting Telstra Online Support.
The answer is to RESET the Telstra Gateway modem not just turning it off and on.
This is achieved by pushing a pin or paperclip into the reset hole at the back of the modem and holding it in until all lights go out and then letting it start.
I also as a precaution turned off Windows Power Management on my wifes computer network card to prevent Windows putting it to sleep.
Thanks for assistance and response.