[fetchmail] lock creation failed

Hi

I have a problem with fetchmail and I'm not sure why this is happening as it
happens only sometimes.

I have a script that does the following:

                OPTS="--syslog -t 300"
                FORUSERS=`awk -F: '{ if($3 >= 400) print $1 }' /etc/passwd`
                for a in $FORUSERS ; do
                        if [ -f /home/$a/.fetchmailrc ]; then
                                su - $a -c "fetchmail $OPTS"
                        fi
                done

But sometimes a file .fetchmail.pid gets created with zero bytes in size and
the next time the script runs it gives the error: lock creation failed

I've checked the Fetchmail FAQ and mail archives on this mailing list, but
not much info regarding this issue. Any help would be greatly appreciated.
Thanks in advance.....

The version of Fetchmail is:

Name        : fetchmail                    Relocations: (not relocateable)
Version     : 5.9.0                             Vendor: Red Hat, Inc.
Release     : 0.6.2                         Build Date: Tue 28 Aug 2001
08:11:35 PM IST
Install date: Tue 09 Apr 2002 05:40:00 PM IST      Build Host:
porky.devel.redhat.com
Group       : Applications/Internet         Source RPM:
fetchmail-5.9.0-0.6.2.src.rpm
Size        : 1033495                          License: GPL
Packager    : Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>
URL         : http://www.tuxedo.org/~esr/fetchmail/
Summary     : A remote mail retrieval and forwarding utility.


This is running on
Red Hat Linux release 6.2 (Zoot)
Kernel 2.2.14-5.0 on an i686