Don't know if this issue has been resolved or not but I was having the same problem and solved it
I found this thread by way of Google, so hopefully I can help someone that was having the same problem as me
Since I'm new, I can't post any screenshots or links, so I'll try to be descriptive, but its kinda the same method from crabman post
Samsung Galaxy s3 T-Mobile
So, this is how I came about the problem. I downloaded a playlist backup app that also make a .nomedia file along with a playlist backup in whatever folder its in. I wanted my playlist backed up on the root of my external SD card, but I didn't know nothing of the .nomedia file at the time.
The app put a .nomedia file on the root of my extSD card
Don't bother trying to find the file with the stock file browser because its hidden. You'll need something like Root Explorer to find it.
These are the steps I took
>Using Root Explorer, find the .nomedia file on the root of your extSDCard and delete it
>Go to your settings and open up the application manager.
>>>Force Stop and Clear Data from two apps, Music Hub and Music Player
>Unmount and Mount your extSdCard
>Restart your phone
Oh, I also pulled the SDCard, but I don't think it was necessary. I hope this helps someone out that was having the same problem as me.