Q: MacBook Pro won't read Sandisk SDHC cards since Lion 10.7.1 update

I have 10.8.3, Mac PowerBook, and I got my 32 GB Sandisk to work without downloads or upgrades. The disk mounted fine, I could see the icon on my desktop when inserted, but a slashed-pencil icon in the upper left corner of the window suggested it was write-protected. It would refuse to copy when I'd drag and drop.

I went to Applications > Utilities > DIsk Utilities, and "Erased" the disk. Be sure to choose Mac OS as your format. It even allowed me to rename it from "No Name." I'm transferring 28 GB of music as I type this, to play in my car. 

Oh, and make sure the mechanical write-protect toggle (on the disk's plastic cover, on the left side) is clicked into the up position. This throwback 'feature' takes me back to mini "floppies" and putting tape over the little hole...

Perhaps try reinstalling the latest combo install of your version of OSX -

could.be a driver permission error or a faulty reader if new

The WD40 trick only applies for out of warranty known to have worked gear

If it hasnt worked or broke in warranty take it to apple and they should.replace it without charge if on apple care

Hi Supritha, Just to say THANKS YOU!!
I had the same problem, downloaded X11, installed (did not work), restarted and Voila... allmy SD cards are now mounting perfectly.
I can't explain, how on earth these 2 things are related...
Again, THANKS YOU

I am on Mountain Lion, 2008 MacBook Pro, using an 8GB ScanDisk. Earlier today, I uploaded photos no problem. A couple hours later, nothing at all pops up on my computer.

I had X11, updated it, didn't work. I've reset, shut down, scoured the forums to no avail. I've tried inserting it part way, nothing.

It was fine earlier today, and now it won't read it? What am I doing wrong?

Meh, I was able to connect my camera directly to my MBP with a USB cable. Originally, that didn't work, but I realized I had to turn ON the camera when I did that Still didn't solve my memory card problem, but at least I can upload my images this way.

I have been having this SD card problem ever since I've upgraded to Mountain Lion, but that might just be a coincidence.  I was on 10.8.3, SD card was working, had a RAM and HD upgrade, and the installed version on the HD was 10.8.4, SD card stopped working, upgraded to 10.8.5, meanwhile doing all the other tricks mentioned here, like inserting the card slighty all the way,and for a while, it worked.  Then it stopped working last night. 

My XQuartz was already updated even before 10.8.5, so that wasn't the culprit.  I tried resetting PRAM and SMC, upgrading the SMC and EFI firmware (they have been hanging since a few months after I got my MBP Pro 15 late 2011) and tried the other tricks I found here.  It's either a software problem or a hardware problem.  The System Profiler can see the SD Card Slot, it's just not reading the card right.

I found this googling Mountain Lion SD card slot fix.

https://discussions.apple.com/thread/4918957?start=0&tstart=0

This is a more intrusive (but still rather safe, so as long as one is really careful) way of doing it.  My next move was to get a can of contact cleaner, but I wanted to try other things out first. 

It's not just dust, but grime (or oxidation on the copper/brass contacts), that accumulates over time, especially when the card slot is not in use for long periods of time.  Contrary to the claim though, toothpick trick actually doesn't do anything but clean the contacts rather than "flick" a switch in the slot.  The two "thinner" contact points on the right side of the SD card (facing you) connects the contact points of the slot, powering the card, nothwithstanding, if any of those data contact points become dirty, the card won't be read fully if at all.

I've tried it, and it worked.  When it worked previously, it might have been that the SD card I've been using inadvertently "cleaned" the contact points while I repeptitively inserted and removed it.  After a while, more grime accumulated so much that not even repetitive insertion and removal did it anymore.

Hope this helps you guys.

Also, it's possible that the contact points themselves got "stuck down," and using the toothpick dislodged it.

I have MBP 17" with ML 10.8.5 and can only read SD cards in my Kingston Card reader. If I use an generic SDHC only reader it only reads the card if the are formated EXFAT and not FAT32 which my camera needs.

I have two 16Gb SANdisk and 1 8Gb transend. All work in Kingston but not the generic readers. I reset the SMC which did not help. I removed and re-installed xQuartz and I could read the disk once. After that it fails again. Most of the time the generic card reader does nothing. If I am lucky it says it can read the disk, initialize or eject. Any tips welcomed as finding anothe Kingston reader might be difficult.

try the toothpick trick.  the contacts may just be stuck or too low for the card contacts to reach.  just be careful.

Thank you for the tip but I dont think the toothpick trick is the answer. I have two of these genric usb SDHC readers and they both only read cards if they are formated EXFAT. This would suggest the card readers can read the card but OSX or the reader or both can't read FAT32.

The card readers both read FAT32 on an iMac running 10.6 or Windoz laptop.

And my MBP reads FAT32 on a kingston 15-1 card reader.

check it anyways.  I had an issue of cards with format problems before (one was Canon which can be read, the other was Nikon), but, now both can be read after the toothpick trick.

Resetting the PRAM worked for me. Hoorah!! 

(Then be sure to unlock SD card if you want to copy it)

For me it was a bad adapter: SanDisk 32 GB SDHC... Thanx to Thunar and all his colleagues I had another adapter...

pfffff sweaty forehead

I have the opposite problem.  My 2013 MacBook Pro will read my 16GB microSDHC card in the SD slot with adapter, but not will not notice it via USB adapter...  Strange thing is that my 2008 MacBook has no problem reading/writing the card via USB.

I have a new i7 iMac and this is my experience thus far using my Sandisk ImsgeMate All-in-One card reader while trying to read my 8GB Extreme III compact flash card:

The card mounts  to the desk top as it should.  When I try to download the images to a folder ( as I have a million times previously) it does so very, very slowly then the reader icon self-ejects followed by the following error:

Then within 30 seconds or so, the reader icon will re-appear.  Attempting to download the images ends with the same results. 

I have tried using a 4GB card, but that card never even appears on the desktop.

This is EXTREMELY FRUSTRATING  and one would think that Apple would drop in with some suggestions.  The blame could also fall squarely on Sandisk's lack of driver support.  Their Mac download page mentions some issues with Mtn. Lion, but if that is the best they can do then therein lies the problem. 

I have no idea what the solution to this is.  I wish I did.

Thoughts????