When I try to log in to the cluster, I get an error message like “incorrect password”.

Your initial password should be right. Please make sure that you are typing it correctly and that you aren't getting extra characters before or after the password if you are trying to copy and paste.

I was running a long stata program with command

nohup stata-mp -b do dofile.do &

, but the job got killed after I exited the cluster.

Try typing exit or CTRL-D in the terminal to log off the cluster cleanly instead of directly clicking the red X in the upper right corner of the ssh client window to exit.

Whenever I try to copy any file to my folder in the cluster, I receive this error:

General failure (server should provide error description).
Error code: 4
Error message from server: Failure
Request code: 4

I already unistalled and reinstalled WinSCP, and it does not solve my problem.

This type of problem usually occurs when you exceeded the disk quota (17G per user). To examine your quota usage, type 'quota' and look for the number under blocks. Users using FTP software other than WinSCP could encounter problems of failing to transfer file onto cluster without an error message. Try using 'scp' to transfer file to cluster, and if disk quota is full, you will get an clear error message saying so.