"From:", "From:" -> "FFrom:", "rom:"

Since implementing Procmail V3.10 (AIX V3.2.5, ipop3d
V3.3(20), NO_fcntl_LOCK, NO_lockf_LOCK, NO_flock_LOCK), some mail gets
munged such that the "From:" headers from two consecutive notes get
changed to "FFrom:" and "rom:".

When I look at a number of our 8,000+ mailboxes, everything looks just
fine. When I look at the few affected mailboxes, I cannot see anything
wrong with their permission bits. While a couple of mailboxes have had this
problem occur several times, inbetween emptying out the mailbox, there are
times when all of the "From:" header lines are just fine.

I replaced 'bellmail' in Sendmail (AIX V5.?)  with 'procmail':

        Mlocal, P=/usr/local/bin/procmail, F=lsSDFMhPfn,
                ... A=procmail -a $h -d $u

I occassionally get 'Lock failure on "/usr/spool/mail/<userid>.lock"',
messages for return receipts.

I am more concerned about the munged "From:" headers. Anyone got any
ideas? Thanks.