So, I installed Enderal and it ran fine, for once.
Then, I installed the last release of Wrye Bash (Wrye Bash 307 Beta3 - Standalone Executable - 1840) from Nexus, just to see, not thinking about installing mods for the moment, and obvioulsy I've set it up for Enderal, as I did for the old Enderal release. Since then I've never been able to get to the menu, achieving the runtime error message you can see in the attached screenshot.
Obviously, I tried a lot of things: re-downloaded and reinstalled all, had Steam verify the files integrity, uninstalled Wrye Bash completely, reinstalled the Visual C++ Runtime (in the Steamworks Shared\_CommonRedist folder), ran the game as admin (actually, this one was weird, it launched Skyrim instead).
Nothing worked. Even after the last patch, nothing changed.
So, I'm wondering what's the problem with Wrye Bash, that by the way is running very fine in Skyrim (and Skyrim itself keeps running fine, too, as did the old Enderal release).