WinSCP, running on my Dell laptop, was open and connected to my target platform. I needed to transport my laptop to another location, so I simply minimized WinSCP and other open applications, closed the monitor, unplugged power adapter and other peripherals. Took laptop to new location, opened it, and used it under battery power. When done after a couple of hours, I returned to the original location, but waited until next day to reattach peripherals and power, then power up. When the laptop came up, the attached error message was being displayed. I acknowledged the error and re-opened the minimized WinSCP (it had not been shutdown the entire time ... just minimized). I reconnected WinSCP to the target, and it's all working as if no problem had ever occurred.
Invalid access to memory.
The problem happens rarely. I cannot reproduce it.