SD card slot is always read-only

I have a 4 GB Micro SDHC card and I use a Micro SD adapter sleeve to read it with the built-in SD card slot of my 15" mid-2010 MacBook Pro. It's been a while since I tried to use it, but I just realized that my Mac will always treat it as read-only, no matter the position of the physical lock on the adapter sleeve.

I can't even format the partition because all the options in the "Erase" and "Partition" tabs of Disk Utility are grayed out for the SD card.

Why is the card read-only, and more importantly, how can I write to it?

Solution 1:

In my case, a physical misalignment is causing the read only status. Gently pushing the disk away from the display reliably makes my cards write again.

Solution 2:

Slide the read/write lock to the middle neutral position and retry. I have the same problem sometimes...

Solution 3:

The problem spontaneously disappeared for me. I'm leaving this as an answer since it might reassure some people to know that for some random reasons, at some point, things start working again. However, I was not able to pin down a specific cause for it, so I'm not going to accept the answer, in case that at some point someone comes with a rational explanation.