Cannot Update to 3.8 or Activate

I am trying to update to 3.8 and the update fails because “Update Failed: Could not remove the old plugin.”

I can’t Activate the plugin either. I’ve tried turning off all plugins, then running the update, but still the error.

I’ve used this Plugin for many years, this is the first issue I’ve had. I’m worried that if I completely uninstall then reinstall, all the meta data etc for my hundreds of posts will be lost.

TIA