Rescue of unfiltered data

Occasionally while processing a receipe procmail gives the
following error:

procmail: Error while writing to " ($FORMAIL -rt \
    -I"From: ${ALTFROM}" \
    -A"X-Loop: ${NOLOOP}";\
    cat ${SBDIR}/msworddoc; \
    sed 's/^/> /g' tmsworddoc; \
    ${RM} tmsworddoc) \
    | ${SENDMAIL} -oi -t"
procmail: Rescue of unfiltered data succeeded

The reciepe is:

:0 BHh
* ^Content-Type:.*application/ms 
{
:0 c:
| $FORMAIL -A"X-Sorted: Microsoft application" >>$CLIVE 

:0 c:
tmsworddoc

:0 f: tmsworddoc.lock
 | ($FORMAIL -rt \
    -I"From: ${ALTFROM}" \
    -A"X-Loop: ${NOLOOP}";\
    cat ${SBDIR}/msworddoc; \
    sed 's/^/> /g' tmsworddoc; \
    ${RM} tmsworddoc) \
    | ${SENDMAIL} -oi -t
}

I dont understand why it works most of the time, but occasionally
procmail chokes on it. 

The idea of it that it matchs on an ms applicattion content-type
line. Then appends a copy in $CLIVE which is a file. Saves the body to
another file. Then produces a reply to the sender with a helpfull
message explaining why we don't accept microsoft attachments and
appends a quoted copy of the original. Maybe there is a better way of
doing this?

Thanks for any help or guidance.
Beth