OK.
So here is the outcome.

usbnet linkage from balloon to a desktop/laptop probably requires that desktop to have a "modern" kernel.

Mine are both lenny (2.6.26) and this is an old kernel.

If you are trying to build and program a system using trunk checkout (not menuconfig2 as I erroneously stated in a previous post) and you would like to interact with an old desktop then you probably can't use the "out of the box" build.  I say probably because I'm not in a position to try it as I don't have a "modern" kernel desktop.

I found that most of the problems I was encountering have gone away by using the CUED configuration of Balloon board. This configuration has a setting for RNDIS compatibility with old Kernels but that can't be the whole story as this has also made memory sticks work, which is how I finally programmed up the board I'm working on. This could be because it includes FAT support, or other stuff that is included with the CUED build, it would be interesting to diff the configs and work out the real difference.

Even though there is now connectivity between Balloon and desktop programming over usbnet is a bit painful as there is no ssh support in initrd (apparently wget or netcat should work but I didn't try them) and dropbear is gone.

The general conclusion is that the "out of the box" build is less useful for people who don't want to have to upgrade their desktop machine in order to program Balloon boards. (It's a couple of days I just don't have).

Interestingly none of the wiki pages about programming up a board tell the whole story so I will now endeavour to create a definitive page with all the runes that just worked for me.

There is also a need for better cross linking on the wiki in this area so I'll try and improve that at the same time.

Kind regards

David