This error is caused when the game needs a file, but that is in-use by some other program.

If you encounter this error, you should make sure you don't have multiple instances of the game open, that could be interfering.

Otherwise, you should check if you have any program running that could possibly be using those files, or try to restart your computer and see if the issue persists.

In event that this fails, you may need to reinstall Minecraft.

As a last resort, you may change the work directory that Minecraft uses entirely.