hidden files on micro sd card

i have a r4i flash cart from r4igold.cn and a toshiba micro 4gb sd my dsi is 1.4u. now my flash cart doesn't work and when i put my micro sd into my computer it says this folder is empty but when i go to add anything to it, it is full. is there any way to get back all my saves off of it and is this a good flash cart? i appreciate any help. thanks

There must be some problems with your micro sd card , you need to format it and then try if it works.