[Exim] exim POP account locking

Hi,

We house a clients mail server here that runs exim 2.01 soon to be updated
to version 3.12. Every so often there is a problem logging into the account
using POP3, it continually asks to re-enter the correct password which I
know is correct because using telnet with those details and then using pine
I can log in OK and read the mailbox. The error message I recieve is that
the mailbox in /usr/spool/mail/user is already in use although I know it
isn't. Is there an easy way of removing this POP lock to allow access to the
account ??

Cheers

Matt James