Qmail Authentication problem

Hi there,

I'm runing Qmail on FreeBSD with virtual domains and Maildir
configuration. I'm using checkvpw for the authentication and tcpserver
to run pop3d.

Everything was working fine, until yesterday all over sudden
authentication failed and nobody could login to there mailboxes.
Meanwhile, qmail is working: receiving emails. The error message that
I've got is:

There was a problem logging onto your mail server. Your Password was
rejected. Account: 'xxx.com', Server: 'xxx.com', Protocol: POP3,
Server Response: '-ERR this user has no $HOME/Maildir', Port: 110,
Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC92

Does anybody knows what's going on