This sounds like somehow the text file has become write-protected. One thing that can cause this is if you are running two copies of Toolbox. Another is if Toolbox crashed -- when Toolbox runs it write-protects the files it has loaded. If the computer crashes, Toolbox doesn't always get the files un-protected.
Anyway, if the problem is the file is write-protected, the solution is simple.
Close (all copies of) Toolbox.
Using Windows Explorer, navigate to the folder containing your project. DO NOT ENTER the folder.
Right-Click on the folder icon. Windows will offer a small menu.
Choose Properties.
Windows will bring up a Properties dialog box. At the bottom is "Attributes"
Click on the Read-only attribute until the box is empty.
You will be asked to confirm
Now try running Toolbox again. You should be able to interlinearize your file now.
If that doesn't work, please let me know.
Karen
Toolbox Support