Problem is solved ! :)
I’ve had a program running (Filebox eXtender) which extends the Save/Save As/Open dialogs with any shortcuts you want for faster navigation, but for some reason it didn’t play nice with EmEditor. I had more problems with other programs due to this program, I’ve configured Filebox eXtender to not attach it to EmEditor.exe at all, and now everything is fine.
Seems like this Filebox eXtender is no longer developed for a reason, I’ve had to disable it for a whole bunch of programs which it didn’t work fine with.
Sorry for bothering you once more with a problem that wasn’t related to this fine Editor.
Thanks again Yutaka !