I have restarted the computer, deleted the WinSCP.ini, re-downloaded the WinSCP 5.7.7 to make sure there wasn't a bad download. Entered the correct server and credentials, saved the credentials and clicked Login. WinSCP threw a Windows error messagebox.
Title: Error - WinSCP
Icon: Red X
Message: gethostbyname: unknown error
Buttons: OK, Reconnect (30s [timer]), Help

I pinged the server and was able to resolve the name.

I created and saved a new connection using the IP address instead of the hostname. Tried to connect to the new connection and WinSCP threw this error messagebox:
Title: Error - WinSCP
Icon: Red X
Message: Network error: Invalid argument
Buttons: OK, Reconnect (30s [timer]), Help

I am doing this in the computer lab, and ten other students are able to connect to this SFTP server. I was able to connect to the same SFTP server from home this weekend.

Deleted a connection while in the middle of creating a new connection (I was recreating a connection that was unable to gethostname.)

When I tried to save the new, corrected credentials, WinSCP threw the message.

WinSCP 5.7.7

Error message:
External exception C0000006

Stack trace:
(007DF82F)
(0005A5DA) ntdll.dll
(0000F12E) ntdll.dll.KiUserExceptionDispatcher
(0075ECC3)
(0075EEA3)
(0021C609)
(00185074)
(0021C76F)
(0021C609)
(0021BC50)
(0034059C)
(000152F7) USER32.dll
(00015D35) USER32.dll
(00018669) USER32.dll
(000186D0) USER32.dll.SendMessageW
(000A359B) COMCTL32.DLL
(000A35FE) COMCTL32.DLL
(000A3488) COMCTL32.DLL
(000152F7) USER32.dll
(00015D35) USER32.dll
(0001FD32) USER32.dll
(0001FD58) USER32.dll.CallWindowProcW
(0021C71A)
(0021C609)
(00185074)
(0034059C)
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167CE) USER32.dll
(00016895) USER32.dll.DispatchMessageW

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.