Having the same issue as above ~sometimes~
All scene images hosted on AWS, cors policy set, headers OK etc. Tile images fine - just the thumb.jpg file will fail to load sometimes with a CORS error.
Note that when the thumb fails to load in KRPano - I am loading the thumb image elsewhere on screen at the sametime in a regular <img> html tag which works fine.
So CORS error occurs on <scene> .....thumburl="url"</scene> and OK on html <img src="url">?
Maybe I am missing something...
Thanks