Sure enough, I was able to successfully transmit and program 4.9 into my Indigo and I followed instructions and turned it off for about 30 second following the successful completion of programming. I even held the LFO buttons to reset the machine.
It appeared to work but the keyboard goes nuts. It misses notes or they stick. Quite useless. I think this is a problem for early versions of the Indigo and KB which had keyboards controllers that weren't quite fully baked. This becomes especially apparent on later versions of software that started using the keyboard data at an apparently higher rate.
I am at the moment trying to load 4.52.