OS? if using Mac or GNU/Linux I suggest that you double check file permissions.
Otherwise, you can play with the settings in the latest 10.x regarding the file extensions.
The encoding, if different between the 2 sites at mysql collation, db, table or content level might be interfering
Otherwise, no more clues.
The files are stored as hash-based names, with no extension, that's true (that's the default behavior, and it usually works well with no problems).