Shhhh everyone will want one!
Just kidding...I don't know why you have that red X, but you do see that when Windows can't reach a resource. Is there a chance that you remapped that area from the C drive to another drive and now that 2nd drive is offline somehow?
I know a few of my customers got into a real pickle when an employee decided to log in to her personal Microsoft account on a work computer and all the files on that computer started uploading to her Onedrive account. All the files were literarily leaving the computer to live in the cloud. Those files were shared on the network and suddenly no one could find their files.
I wonder if that is what happened to you too?.