[imp] redirect.php error & login failure - data dependent?

[Steve Lidie]

With a few thousand users, I have 10-20 that cannot login to IMP, they 
get an error mentioning that accessing redirect.php failed.  I've seen 
similar reports in the archives from 2001 using PHP 4.0.6, but no 
resolution.  I'm using 4.2.0.

I found that using Netscape I am able to read 4 of 4 pages of the 
user's mail.  Amazingly, when I tried IMP afterwards I was able to 
login, but could only see 3 of 4 pages of inbox mail.  Trying to goto 
page 2 always gives:

    The attempt to load 'Accessing URL: 
https://hostname/horde/imp/mailbox.php?page=2' failed.

This, essentially, is the same error message I had previously seen when 
login would fail.  The archives mentioned imap_sort() getting a 
segfault... could this still be the problem? Regardless, is this a 
known problem?

Thanks,

Steve