Follow the below directions:
Take your world files and copy them to the desktop.
Copy them to a side folder for backup.
Delete your entire .minecraft folder.
Delete your Minecraft.exe file.
Uninstall all versions of Java you have installed, I recommend using this.
Install only the recommended version of Java for the version of Millenaire you are using.
Install a new Minecraft.exe file.
Run Minecraft.exe, close.
Move your world files back.
Run Minecraft and try it now.