Grasshopper error upon startup

I just switch back to Windows after having Macs for over a decade. Here I am, already running into issues. Rhino is up to date, as is Panther. That is the only two plugin I have installed.

I keep getting this message upon startup:

Message: The process cannot access the file ‘C:\Users\xxxx\AppData\Roaming\Grasshopper\PluginLoading.txt’ because it is being used by another process.

What does this even mean? And how do I fix it?

I am unable to use Panther or Rhino with this issue.


Hi Stephanie - if you remove Panther, does it all work?


It does. I uninstalled both. Reinstalled Rhino. No error upon startup. I then installed Panther and am getting that error.

I never saw this error before while running boot camp windows on my Mac, but now running on windows I’m having this issue. Not sure if there is a setting or programming thing about windows that is throwing this error? I don’t know enough about this OS :slight_smile:

Hi Stephanie - I think I’d start with the developer for Panther.


I’ve tried. Was hoping it was some other issue, since it operates differently on bootcamp. I’ll post an update for anyone else experiencing this once I get through to support and find a solution!

Stephanie, I moved this topic to the Panther forum - we’ll see if the developer takes note.



I am receiving this error alongside many colleagues of mine. The native objects are not loading. we are not using Panther but we have many plug ins… using rhino 6 and i just started getting this error as of this morning.


FWIW, i reverted to previous versions of Rhino 6 and Rhino 7. All is once again well.