After a fresh install of minecraft all the chests changed color to red/green with a white cross and all inventory in all the chest over whole map disappeared. I have installed on multiple machines and the issue persists. I had all my saved games backup but I can not use the backups at all. This is not my online games but single player maps. I have spend years building these maps and do not want to lose all that I have build up in this time.
The changed color is a normal thing (for december 24-26), see the wiki.
The lost content is not normal. Did you do anything else that might have contributed to that (e.g. changing the version of the game)?