I see a lot of posts like this when the drive is USB 3.0. The user will always claim USB 3.0 is backwards compatible and you can't help them. Try an USB 2.0 drive.
....and I can play AVI, MP4 etc movies that I added to my USB stick on the TV no problem, but I have since added all my movies to an Hitachi Touro 1tb USB 3.0 drive and when plugged in, every single file says 'this file is invalid'
Is it a formatting problem? I have a MacBook Pro but the drive, as with the USB stick, are formatted it to MS-DOS (FAT32) and one works, the other does not.
Can you please let me know why this might be?