@colrose could you try it after removing `C:\Program Files\GTK2-Runtime Win64\bin` from the PATH? Geany should use its own bundled GTK+ since it's in the same directory as the `Geany.exe` executable, but it would help rule out that it's trying to link up with a wrong version of GTK+ or one that was compiled with a different calling convention/ABI. Both you and @DiepEsc seem to have other GTK+ runtimes in your PATH, so it might be related.