Thanks very much for your help - in particular your suggestion to redirect the output of pscp. It turned out that the cron replacement I was running launches programs as a different user to the current one, so when pscp was exectured it looked for a cached server key in the registry that didn't exist for that user. I changed it by going into Services and changing the 'Log On As...' options for it. The thing I changed in the last month was reinstallation of the cron replacement. Thanks again!