Thx for using Fusion!
What's the version of standard VMware Fusion you used? Is that 6.0.x?
If you use Fusion 7 Preview version to open a VM with Fusion 6.0.x tools, then after VM started, vmware tools will be updated automatically underlying. Will prompt to you to restart VM after update completed. If you try to install vmtools manually at the time underlying update is going on, it will tells you that another install instance is working, can't start another installation as you request.
And do you try not to reinstall tools from VMware Fusion's menu item, but to uninstall tools from Windows' control panel, restart VM, and then to install tools? Does this work?