There could be many causes. Here are a few:

• Restricted host: some hosts in our network are not for public use, but only allow a subset of the MathNet user base to log in. If you need access to non-pulic hosts, contact the IT staff.

• Misspelled password or username: if this is a newly created account, it's possible that your account name or password is not what you remembered it to be.

  Also, if your password has numbers, it possible that you have entered your password (either when setting it or entering it) using the numeric keypad. The numeric keypad may or may not have been configured to enter digits (e.g. NumLock). Always use the keyboard top row when entering digits unless you are certain the numeric keypad is set for numeric use.

• Keyboard: sometimes a button is sensitive (double characters), broken or perhaps is mapped to something other than what you expect. Try typing your password using this keyboard into a window which you can see your keystrokes (while no one is looking, of course) and see if what you type is what you expect.

• Quotas: if you have filled up your allotted file quota, the login will see to be partially successful, but then will log you back out. If you suspect this, you will have to contact the IT staff or perhaps log in via ssh and delete some files. See elsewhere in this FAQ about how to check your quotas.

• Screwed up login scripts: if you have recently modified your login scripts (such as .cshrc, .login, .profile, .xsession, etc) then errors may cause your logins to be aborted. If you are logging in to a graphical desktop (i.e. not a command line interface), you're desktop might be screwed up: you may have to re-install your desktop.

• General network problems: if the host you are logging in to has no network connection with the authentication server, the host cannot authenticate you and thus cannot log you in.

• Administrative mistake: it happens (really!).

• X-terminal amnesia: if you have a graphical terminal, and a network problem happens, they sometimes needs a power off/on to get it back to a working state.

• Windows host insists on 8 character or longer passwords:
  see FAQ entry on this topic.