I have an Adafruit Micro SD Breakout Board attached to an Arduino MEGA2560. Running CardInfo I couldn't get the card to initialize. I triple checked the wiring, tried a few different cards, nothing. Eventually through jiggling all the wires and poking at it in hopes I could find the issue I discovered that if I pressed my thumb against the back of the card slot (as shown in included picture) it would initialize the card perfectly. After I take my thumb off it will continue to recognize the card each time I hit the reset button, as long as I hit it every few seconds. If I wait longer than ~10 seconds it won't recognize it anymore.
I'm assuming that this is some sort of card contact issue, but I have no idea what I'm doing to cause it to succeed.
This is a short in the dark, but you are using one of those cheapo proto boards. Maybe it's just me, but I had grief with them, and it was because of bad connection every time, so look there first. There are good green boards on ebay that are still cheap and the size you require.
Just my guess, I might be wrong but have u tried to ground the metal part of the SD card slot? If that doesn't work then pry to see the solders of the pins of the SD card slot. One of it might be barely touching.