I have an issue with the SD card as well. Actually, the phone doesn't detect SDcard at all, even in recovery.
I've tried mounting USB storage in 4ext, can't do that, can't partition it, format it, anything. The SD card works ok in card reader and camera, so I guess it's an issue in the phone?
This happened after I opened my phone to clean it out. It isn't the first time I'm doing this, but nothing ever went wrong.
It's confusing to me, because I didn't even touch anything around the SD card slot, just removed the back panel, cleaned the upper part of the phone where the speaker is and that's it, I didn't even take the entire motherboard out, no need for that.
Does anyone have any clue how could I fix this?