<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 6.5.3

Error message:
Acesso inválido à memória

Rastreamento de pilha:
(00B9F621) _free_prompts
(00EF5B8E)
(00EF7C06)
(00EF49B0) __ExceptionHandler
(00099A1F) ntdll.dll
(00078491) ntdll.dll.KiUserExceptionDispatcher
(00B94893) _ssh2_userauth_set_transport_layer
(00B9324C) _ssh2_userauth_set_transport_layer
(00B7C589) _ssh_ppl_free
(00B3624E) C4305_0
(00B36341) _run_toplevel_callbacks
(00C9BE45) TSecureShell::EventSelectLoop
(00C9AD57) TSecureShell::WaitForData
(00C95679) TSecureShell::Init
(00C94FBA) TSecureShell::Open
(00CF0231) TSFTPFileSystem::Open
(00D33077) TTerminal::Reopen
(00D3579D) TTerminal::QueryReopen
(00D28010) TRobustOperationLoop::TryReopen
(00D526FA) TTerminal::SinkRobust
(00D524B8) TTerminal::DoCopyToLocal
(00D1F136) TSFTPFileSystem::CopyToLocal
(00D51FC7) TTerminal::CopyToLocal
(000123AD) TCustomScpExplorerForm::ExecuteCopyMoveFileOperation
(00012E9C) TCustomScpExplorerForm::ExecuteFileOperation
(00013118) TCustomScpExplorerForm::ExecuteFileOperation
(0002762F) TCustomScpExplorerForm::RemoteFileControlFileOperation
(00027A65) TCustomScpExplorerForm::RemoteFileControlDDEnd
(0050A361) Customdirview::TCustomDirView::DDDragDetect
(00BB3AC6) TUnixDirView::DDDragDetect
(0050638E) Customdirview::TCustomDirView::CNNotify
(0039E2AA) Vcl::Controls::TControl::WndProc
(003A3455) Vcl::Controls::TWinControl::WndProc
(0041AF67) Vcl::Comctrls::TCustomListView::WndProc
(003A35AF) Vcl::Controls::_17122
(003A3455) Vcl::Controls::TWinControl::WndProc
(003A2960) Vcl::Controls::TWinControl::MainWndProc
(00204B78) System::Classes::_18364
(0003290D) USER32.dll
(000232E1) USER32.dll
(00022D5B) USER32.dll
(0002CEDD) USER32.dll
(0007844B) ntdll.dll.KiUserCallbackDispatcher
(00039B5D) USER32.dll
(00021D01) USER32.dll.SendMessageW
(00098C86) COMCTL32.DLL
(001BCF33) COMCTL32.DLL
(00092C17) COMCTL32.DLL
(00091BF2) COMCTL32.DLL
(0003290D) USER32.dll
(000232E1) USER32.dll
(00022BA2) USER32.dll.CallWindowProcW
(003A355D) Vcl::Controls::TWinControl::DefaultHandler
(00508096) Customdirview::TCustomDirView::WMLButtonDown
(003A3455) Vcl::Controls::TWinControl::WndProc
(0041AF67) Vcl::Comctrls::TCustomListView::WndProc
(00204B78) System::Classes::_18364
(0003290D) USER32.dll
(000232E1) USER32.dll
(00022BA2) USER32.dll.CallWindowProcW
(0007DA14) COMCTL32.DLL
(0007DAB3) COMCTL32.DLL
(0007D82C) COMCTL32.DLL
(0003290D) USER32.dll
(000232E1) USER32.dll
(00022BA2) USER32.dll.CallWindowProcW
(0053941F) Dragdrop::TDragDrop::WndMethod
(00204B78) System::Classes::_18364
(0003290D) USER32.dll
(000232E1) USER32.dll
(00021AE3) USER32.dll
(0002164B) USER32.dll.DispatchMessageW
Log de autenticação (veja sessão log para detalhes):
Usando nome de usuário "CORPORATE\penegreiros@prd.intraservice.corp\penegreiros.cl@admcor70002p".

Autenticação falhou.

The problem happens rarely. I cannot reproduce it.