Minecraft will not launch

When I try to start up anything, the launcher gives me this error.

"The game directory is invalid or inaccessible.
Error details: The process cannot access the file because it is being used by another process
Filename on disk: .minecraft
Path: C:\Users\William\AppData\Roaming\.minecraft
Exists: directory"

Notes: This started happining after the switch from the old laucher (the one that didnt have the skins tab) to the new one (the one with the skins tab)

I know this looks like a duplicate of MCL-5367, but I uninstalled my antivirus, and it still had the error. I do not know how to fix the problem based on the duplicate case.