Amazon Cloud Player just won't play the songs and fails silently.
Windows media player says: "Windows Media Player cannot play the file. The Player might not support the file type or might not support the codec that was used to compress the file."
Xbox Music says: "Can't play. Make sure your computer's sound and video cards are working and have the latest drivers, then try again. 0xc00d11d1 (0x80070241)"
I'm not sure if this was caused by upgrading to 8.1, but these files have all worked before.
I couldn't find anything helpful on Google. Any ideas?