Isso provavelmente é causado por um dos seus scripts de login na máquina Ubuntu que está gerando a saída para os locais para os quais ele nunca deve produzir. (É como usar a pia em vez do banheiro ... Aposto que o seu colega de quarto ficará sem tolerância em breve.) O PuTTY tem uma seção de perguntas frequentes sobre isso. Leia aqui .
Resumo:
A.7.6 When attempting a file transfer, either PSCP or PSFTP says ‘Out of memory’ and dies.
This is almost always caused by your login scripts on the server generating output. PSCP or PSFTP will receive that output when they were expecting to see the start of a file transfer protocol, and they will attempt to interpret the output as file-transfer protocol. This will usually lead to an ‘out of memory’ error for much the same reasons as given in question A.7.5.
This is a setup problem in your account on your server, not a PSCP/PSFTP bug. Your login scripts should never generate output during non-interactive sessions; secure file transfer is not the only form of remote access that will break if they do.
On Unix, a simple fix is to ensure that all the parts of your login script that might generate output are in .profile (if you use a Bourne shell derivative) or .login (if you use a C shell). Putting them in more general files such as .bashrc or .cshrc is liable to lead to problems.