I don't know about this WinSCP. I use cygwin's command-line scp without problems. Maybe you want to try that? Cygwin is indispensible anyway, if you don't have it yet, get it. When you install, you get a configure GUI and you need to enable the openssh
The other thing you could try to pinpoint the cause problem is to scp a file from the redhat box to itself, using not localhost, but the actual IP. If that works, it looks more like a problem with WinScp.