service not available

I cannot get tivo to update over the internet - service not available. Am using Bigpond wireless 21 modem and wireless network from pc to tivo, ad-hoq network, windows 7. Can transfer files to and from tivo/pc with Tivo desktop 2.8. Can access internet on pc, but tivo cannot access internet.
My internet connection is set to share.
This configuration has worked previously. It appeared that Bigpond connection manager had a problem, but the connection manually setup did the job.
Have set all the ports suggested on the error message to 'open' and have uninstalled all anti-virus software and turned off windows firewall - still no success.
Am completely at a loss - any suggestions.
Peter M

Did you manually setup the TiVo networking or is it set for DHCP?

Peter.