Let me get things straight:
There is nothing wrong with the driver that MD wrote.
There is a problem with the networking stack in Risc OS.
This problem didnt showed up earlier since the risc pc's do not operate on the same speed as the Omega does. And the fact that there is a SA in the Omega and in your RPC's does not make them the same computer. A man with your qualifications should know better ;-]
Both Md and ROL are not to blame for this because that particular piece of the internet stack was written before ROL started working on Risc OS.
So youre conclusion on that there is something wrong with the driver is very "kort door de bocht"