If you get this error when trying to create a new document or to edit an existing document using LocoScript on your PCW, it probably means that the memory of your PCW has become faulty.
Literally, the error means that the copy of the SETTINGS.STD file held in memory has been corrupted. As this file is read from your start-of-day disc (and checked whilst doing so), this means that the corruption has occurred since the file was loaded into memory. The most likely cause of this is that the memory itself is faulty.
To check more definitely, run the RAMTEST program. This is included on every LocoScript 3 or LocoScript 4 master disc and on Amstrad's master discs for the PCW models with 3½" disc drives. Instructions are in the LocoScript 3/4 Installation booklets. If you need a RAMTEST program, LocoScript Software can supply one for a nominal charge, currently £5.
If your PCW has any add-ons plugged into the expansion port, also try running the RAMTEST both with and without the add-on. Remember, ALWAYS turn off the power before plugging or unplugging anything in your PCW.
If the RAMTEST shows no errors then it is likely that your LocoScript start-of-day disc is faulty.