I'm using the built-in SD card reader on a Macbook Pro (15", late 2011) running Yosemite, and it treats every SD card as write-protected regardless of the position of the physical switch on the card.
Apparently this is a fairly common problem. I've already tried all the solutions given in this question, with no success. The only thing left that I can think of to try is making physical repairs to the drive. Since this problem is likely caused by a malfunctioning sensor for a setting I don't care about, that seems like overkill if there is a way to do it in software.
Is there any known way to tell the drive or the OS to ignore the write-protection setting and treat a protected SD card as writeable?