Thanks for your quick reply 
> > I can successfully create a mod launcher (.exe), it runs ok ; but whenever I click on "Activate Mod" button, nothing happens... I have to kill the XCC process, and then switch back to gamemd.exe process manually.
> Switch back? The game shouldn't be running when you activate the mod.
Hmm, maybe have I used the wrong terms...
When talking about the mod launcher, I meant the one generated (or "exported") with XCC Mod Creator ; you know, the one with possibly a customized background image.
Here there is an "Activate mod" button, which a while ago worked properly : it copied the mod files to RA2/YR directory, and then run the game.
I know that it used to work that way before, and with the exact same version of XCC Mod Creator/Launcher...
As previously stated, now it does copy and run the game (since I can see in the Task Manager) ; but instead of showing loading screen, the system is stuck on the mod launcher which "does not respond".
And just in case, by "switching back", I meant Alt+Tabbing or simply clicking on the Task Bar.
I will check this ASAP, but could there be any problem if you add a file inside XCC Mod Creator, but which is later removed from the file system ? (I mean: XCC Mod Creator keeping in record no longer existing files ?)