I cannot use a USB cable to access my version 2.3.6 phone's SD card with Ubuntu 12.04 LTS
I rebooted and it fixed the problem :-\ [and then several weeks later it occurred to me that I should note this fact here, in case it happens to anyone else]. Indeed, I suspect that my phone was in a weird state and probably I could not access the SD card on any computer at all at that point, regardless of what I implied in the question.