OK, in case anyone's interested, I finally found out why I couldn't update (Thanks Tony): Apparently, the capability to upgrade via SmartMedia was added with v.1.07. Thus, with my "first generation" OS the box did not recognize the file. (Although, for some reason, the internal programming did seem to want to start the process....)
My update using MIDI files went fine. BTW, it would have been nice for Roland to mention this on their software updates webpage. Oh well.