I have the same problem (central european umlauts). When will this patch be included in the real release of WinSCP?
Can you tell me what is your server? I'm curious as this particular problem is not likely to occur for anything else that asian character sets. So it maybe that it only looks like the same problem.
Anyway, you can get "official" version. You need to set "Server does not use UTF-8" to "Off" on SFTP tab of login dialog.