What can I do if a GPF occurs when using Exl-Plan and I can only reopen my file as ead-only?
If you encounter an Excel General Protection Fault (“Illegal operation” stuff) then the file in used is not marked “closed” by Excel/Windows. Restarting Excel will only permit read-only access to this file. Restarting Windows usually sorts out the problem. If it doesn’t, open the file as read-only and save it with another name. If you can write after that, delete the original file and rename new file back to the original file name.