If I try to delete or move the gpk file (job001.gpk), windows won't allow it.
You or a colleague most likely have a hanging process (geopak.exe) in your windows tasks.
Go to the windows task manager (ctrl - alt - del)
Go to the processes tab
End any process named geopak.exe
You may have to do this on other machines.
Or, you could log out of windows, or re-boot.