While this may have been used incorrectly causing a problem (don't know
since I've not been able to get it to work properly),
Consider the following steps:
a) Create a message with two attachments (in this case .doc files)
b) Mail the message to an account.
c) Read the email (in this case, with Netscape) and forward the
    message as an attachment to an account from where you will
    access it via PHP.
d) Now try to read and process the file.
The problem comes in dealin with the multipart/mixed portion that
represents the original message that is now an attachment.
When the call imap_bodystruct($stream, $msgno, $partno) is
invoked, where $partno can actually be any value at all (tested values from
0 to 5), each case causes the Apache process handling the request to
croak.

The configure line from phpinfo() reads
'./configure' '--with-apache=../apache_1.3.23' '--enable-debug=no' '--prefix=/usr/local/apache' '--with-zlib' '--with-imap=/home/thomas/imap-4.7c' '--with-mcrypt' '--with-mhash' '--with-pgsql' '--with-gd=/home/thomas/gd1.2'

The apache error log shows a single line
[Tue Mar 12 00:09:13 2002] [notice] child pid 10813 exit signal Aborted (6)