Lock failure causing procmail to eat mail?

My wife just found a scarely procmail problem:

Occasionally in the Procmail.log file one see the following kind of message:


procmail: Lock failure on "/var/spool/mail/mdsmith.lock"
> From owner-knitlist(_at_)kniton(_dot_)com  Mon Nov 15 23:34:19 1999
 Subject: Knit: knitting groups or clubs
  Folder: /var/spool/mail/mdsmith                    

The mail is then silently dropped.  Gone. Not in any mailbox

Her mail in poped off of a mail server using fetchmail; her mailer is MH.


Anyone else seen this..?

DHMS