Try it on another computer (although that shouldn't be the issue but i've seen crazier things happen) If your chkdsk /r does not solve your problem, You can still recover your data though it may get tricky. I've encounteded this situation many times with hard drives and flash drives/Micro SD etc and what i've been able to do was a quick format of the drive and then data recovery with software such as GetDataBack ( http://www.runtime.org/data-recovery-software.htm ), Ontrack Easy Recovery ( http://www.krollontrack.com/resource-library/free-downl... ) Iolo Search and Recover (http://www.iolo.com/sr/5/) that last one is my favorite when dealing with flash drives.
Now you may be able to use some of this software without formatting your drive first
Many of these with Trials will allow you to recover a couple of files at a time while other trials are going to be fully functional and show you all of the files that the program can recover for you before forcing you to pay/purchase to do so which is very nice actually.
Now these are all risky so depending on how important/critical your data is on this drive you may want to enlist the help of a professional to do this for you because the more you mess around with steps such as the ones i've listed, the less likely you will be able to recover (As in if your formatting and running software over and over again, you may make it impossible for data recovery if you decide to pay more)