I have tried it and I have no problems using password with apostrophe.

Please check server's logs for reason of your authentication failure. Or ask your server administrator.

winscp seems to have a problem with one of my passwords when I enter it using the "session" interface. When I try to log in, after it tries to use it, and apparently fails, it prompts me for the password and it works when I enter it manually.

This happens every time, but only for this one password on this one host, so I'm pretty sure it's password specific.

The only thing abnormal about the password is that it ends in an apostrophe. Is it possible this is causing some kind of problem?