<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 6.1.1

Error message:
Invalid access to memory.

Stack trace:
(0029466B) System::DoneExcept
(00087AFF) ntdll.dll
(00073FD1) ntdll.dll.KiUserExceptionDispatcher
(00214D98) System::Classes::_18201
(0003FE89) USER32.dll
(00036E55) USER32.dll
(00034BC5) USER32.dll
(0003498B) USER32.dll.DispatchMessageW

(00294258) System::HandleAnyException
(00087AFF) ntdll.dll
(00073FD1) ntdll.dll.KiUserExceptionDispatcher
(00214D98) System::Classes::_18201
(0003FE89) USER32.dll
(00036E55) USER32.dll
(00034BC5) USER32.dll
(0003498B) USER32.dll.DispatchMessageW

Status: all_insignificant

The problem happens rarely. I cannot reproduce it.