JTCS won't launch anymore - what is going on?

[Crossroads]

Unfortunately, the issue still comes and goes without making any sense to me.

The issue returned in the middle of testing my OOB files, so I was working with Organization Editor only. All of a sudden, I can't launch East Front.exe anymore.

1) None of the West Front.exe / East Front.exe / Rising Sun.exe work, each one of them ends in black screen after the Matrix MCS video kicks in.

2) If I click at EF.exe directly, I get the 486 error.



3) If I click at EF Scenario Editor or EF Map Editor I get the following message which I don't understand at all.



4) If I click at OOB Editor it opens up but the content is empty

Now,

- I have disabled MS Security Essentials.
- I have updated the video drivers.
- I uninstalled JTCS and renamed the folder left behind with xxx like " \xxxJohn Tiller Campaign Series"
- I reinstalled JTCS and straight after the install it does not work. Yes, the 1.04 patch too.
- CCleaner registry check: no issues.
- Matrix Operational Art of War III works just fine. It is still in the C: drive though.

So it must be a glitch in my system. But I am at complete loss what is going on...