As for the timeout in NavCoder: does ANY response come from the nav?
It may be that the nav has such an old OS version that the responses are different to what NavCoder expects. So send me the NavCoder log file (by email please)

Otherwise, sounds like there is a problem with the flash memory

I would attack the problem like this:

1. Reset nav: power off, power on - by disconnecting the nav purple and blue connectors.

2. Load a OS that is newer than 3-1/20 but not the newest, eg: 3-1/30 or 3-1/40 or so

3. Remember that the new 3-1/63 OS does require a Key CD, so to load 3-1/63 you need to have the Key CD handy

4. Then try loading 3-1/63

If no OS load works, then the flash memory is definitely faulty, and there is not much you can do. Sell it, or use it for spare parts....