Hi once again.
The roku - although in another room - is separated from the wireless router by a book case and pretty thin wall, over about 5 feet. Wifi reception is excellent - it usually shows about 94%.
I'm back where I started. The Roku can see both the FireFly and iTunes libraries, but can't connect to them (this is with the AVG firewall disabled - with the firewall active it can't see them at all).
I know if I drag the roku in the other room, connect it wired, re-boot the computer it will then connect and play songs. And when I drag it back in here, it will connect and play wirelessly. For a while. Then it will die and I'll be back where I am. I'm at wits end with this flower thing and I'm seriously considering putting it up in a cupboard for a year or so and see if it works then.