>>I'm wondering if, although the form is marked as included in the project, it may not actually be written into the .EXE (some sort of .PJX corruption?) or, it was corrupted in the last .EXE build, or the .EXE itself has become corrupted somehow. Any or all of which could lead VFP to believe the form is not present in the .EXE and to go looking for it elsewhere.
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>>A simple experiment: temporarily move the form to another folder; fire up the app and see if you can get into the form. If not, clearly something is wrong with the .EXE.
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>>If it looks like there is an .EXE problem, you could try un-including the form from the project, re-including, then rebuilding the .EXE.
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>I moved the form somwhere else, and the exe runs just fine, so it must be included - which is what I expected.
>Also, yesterday, after the incident, I could start the exe on any station without the .scx getting used, so it was only that station that got the scx. I don't know at what stage the scx was released. I exited the form, and that did not release the scx. Then sombody else closed everything and rebooted... The main question remains: how/why did the scx get used?

Is there any development/"back door" code in your app? For example, I have sometimes written code that works one way if a certain file is present in a certain folder on my development computer. It is extremely unlikely to be present on an end-user's machine but if it was, that code would run instead of the expected code.

Does that user have an old .EXE or other files on their computer?