I am also having what I thought was the regular read only issue but even when I unmount and remount -o rw I still get permission denied. Unless I try as root, then no problems at all. As this is fat32 there shoudnt be any chown issues...
It is not a corruption issue fdisk fsck!!(yipes) comes back clean every time.
Been a long time since I had to deal with unix read/write problems so my magic is weak and google isn't helping.