My guess is the person who is offering the file may have changed or added a description to the file so the file itself is fine.

If your file was unplayable then that would be a different matter.

If you see a brick wall in front of the blue world icon at the bottom of LW's interface then that would indicate a firewall not properly configured.

Oh one option I forgot to add was the possibility of an old modem or router not parsing the data properly.