It sounds a case like you've removed the account entry from /etc/passwd, but it's home dir. has not yet deleted. In any case, that user cannot login, because user identification is done by the system by reading /etc/passwd file. When it won't get user's entry there, it won't allow such non-exxisting user to login.
One more thing, is there using any name services like NIS or NIS+ for central managment of the user accounts, or you're managing them locally, on every system?
Last edited by shivaa; 11-04-2012 at 06:16 AM.