Gil, some drives have a character title limit, the file name can not be above a certain number of characters. If it is stopping at the same song each time try skipping that one see if it makes a difference.
If not, open Disk Utility and select the flashdrive (not the media card) in the left column, select Erase in the upper Tabs and be sure that Volume is not Formatted to Case-sensitive. If it is then change it.
NOTE: THIS WILL ERASE ALL DATA ON THE DISK, so remove any needed or original files.
If still no joy try the Extended (Journal).
Joe