I've now done some testing, and I see that neither double-clicking
nor drag-and-drop was working (or not reliably) for non-ASCII
filenames. I think this should now be fixed in the Windows
snapshot.
I'd just installed the win32 gretl (build date 2009-04-29) and everything is working fine! Thank you!
But I didn't test the Mac OS version yet. As soon as I do this I'll tell you what happened, ok?