I think it has been fixed in v4.3.1.
4.3.0 is bugged even in my Vista 32bits.
This was my post (I have now registered). This does not occur in 4.29, and I now see from the forum that other users have reported this.
Before getting the crash I entered an invalid hostname (domain only without the host part). The crash could be in that code path.
WinSCP 4.3.0 (Build 1029)
OS Windows Vista Home Premium 64-bit SP 2
Just downloaded and ran WinSCP. Enter hostname, username, password and select OK. Invalid Access to Memory screen appears and program exits. This is reproducible every time. My suspicion is that this might occur only in Win-64.
Thanks,
Art