So please switch back to english (Languages button on login dialog). It should work then. I'll post here notice, when corrected russian translation is released.
You are right, I use international version of WinSCP with Russian user interface.
There are no errors with single file operations.
I would bet that you use translated version of WinSCP. Am I right? It this case I need to know the language. If I am not right than I need additional information too. You can probably imagin that, if it were imposible to copy any files as your post suggest, someone would have already noticed (probably even me). So I suppose that there must be some special conditions.
When I mark a few files and try to run Copy or Move commands, I get diagnostic message " Error: No argument for format "%s" ".