This is the first I've heard of a problem like that. It sounds almost like something removed your administrator privileges on your PC.
If I were you I would check to see if you have lost any other privileges regarding your windows security. Aside from that I can only think of doing all the basic security steps to find what caused the problem. (ESPECIALLY if it's ONLY my files that can't be deleted.)
If you need the files removed quickly there's also software that works well with removing files that can't typically be deleted but I have no idea what those would be.