I am using firefly on a NSLU2 (sorry should have mentioned that), so reinstalling on windows is not a option.
Seem's to me that what Ron is saying is the most plausible. But I am not using a firewall on any machine on my local network and the problem started by replacing my linksys WAG54G for the VOIP modem/router Thomson 780 Wi.
So, there must be a problem with the new modem/router but I can figure it out.
So if there is someone out there with a working environment with the same modem and is using firefly with a wireless Roku.......or other suggestions !
Yup, that's it. It must be that that modem doesn't do multicast by default. You can try going into the web interface of the device (if it has one) and seeing if it has an option to enable multicast, or igmp. If it does (either of those options) enable it.
It might be worth checking for a firmware update for that device as well.