Cannot mount SD card, with error "SD card safe to remove" I have an HTC Desire S, which my cousin bought for me from China.

Android version: 4.0.4; HTC Sense version: 3.6; Software number: 1.0.0.S510e

The MicroSD card no longer works. Whenever I reinsert it, I get the message, after a few seconds, "SD card safe to remove". I've tried reformatting it and have run fsck on it.

I think the card used to mount read-only before, as it used to unmount whenever I took a picture; this started happening after the most recent update. I kept trying to take pictures and reinserting the card would fix it but it seems now it won't mount.

How can I fix the MicroSD card so it'll mount?
I'm assuming you mean MicroSD, not SD. Sounds like the card is broken.  You could try formatting it as ext3 or FAT and see if either work.  Also, see if it works on a PC (you can get a MicroSD/USB adapter for next to nothing).