I've a problem with the sd card reader on my reprap discount lcd panel.
I tried with a 2gb and a 4gb (FAT/FAT32 formatted) but I always get "no sd card" on lcd menù. In the info screen I can read when the card is removed or inserted.
I also get a strange behaviour when I turn my printer on with the sd card inserted: basicly the printer doesn't boot and the lcd screen keeps showing the Marlin splashscreen.until I get the sdcard off.
I checked pins, connections, firmware... but I didn't find anything wrong.
Mine was doing similarly, it wasn't until I looked at the solder connections on the card slot with a magnifier, that I noticed a non-contacting solder joint. A touch with a soldering iron, and all's well again.