In response to your suggestions:

- CHCDSK did not find anything
- It failed in Safe Mode which does not have any anti-virus software running
- There are no FoxUser or resource files by any other name.
- A virus/malware scan turned up nothing.

This issue was never solved.

Eventually the IT department at that location decided they had spent enough time trying to resolve this and just replaced the computer. So we will never know what the cause of this was.