Vas and crazyc have been discussing the state of the Rainbow driver in the shoutbox and commented that the driver's not booting the operating system because of differences in the interrupt handling between the A and B models.
On the "B" model, a few ROM patches allow the machine to skip hitherto unemulated parts of the Rainbow. Bavarese has furnished me with the equivalents for the "A" model, and I've issued a pull request for them. This allows the emulated Rainbow 100A to boot from disk cpm860mb.td0, it will also allow mdos201.td0 at least boot as far as the system message, but it will hang after loading track 8.
It appears that at least this CP/M-86/80 image is not yet available, I've uploaded an archive with my Rainbow disk collection to the FTP.
Sorry Robert but I cant' work out from the above whether you are missing the "CP/M-86-80 image" for A or B :-)