I didn't ever delete my firmware, I had just been testing the software upgrade feature.
The only thing I did wrong was that I didn't check that my CD version of the NEWBIN2 fie was the same as the one on my DSP. It turns out it was an older file. It still works fine and I have been using my machine for the last 18 months.
It seems strange to me that the DSP can be corrupted so easily.