[imp] Revenge of the blank folders

[asym]

Hey everyone, new (attempted) conversion to horde/imp here from 
squirrelmail, and I'm having some difficulties that seem to have been 
encountered in the past, though there doesn't seem to be a consensus on 
how to resolve them.

First one, most important, is this:  Sometimes, when clicking on a 
folder to display, the message list comes back completely empty.  The 
header will be there, saying say "Inbox  1 to 5 of 5 Messages" but 
below that there is absolutely nothing.

I think it has something to do with the messages themselves, as I do 
get a lot of poorly formatted spam with garbage characters in the 
headers, or other character sets such as cyrillic.

I haven't been able to figure out a way to resolve the issue, other 
than when it happens logging back in to the squirrelmail install and 
deleting messages, after which horde/imp starts working correctly again.

Relevant installation details:
OS: FreeBSD 4.11-STABLE(i386)
SMTP: Postfix 2.1.5
IMAP: Courier 4.0.6 (courier-imap-4.0.6_1,1 from ports)
PHP: 5.1.1
Apache: 2.0.53
Horde: 3.0.7
IMP: h3-4.0.4
ingo: h3-1.0.2

My horde/imap configurations are very vanilla.

imp servers.php has just this entry:

$servers['imap'] = array(
  'name' => 'Webmail',
  'server' => 'localhost',
  'hordeauth' => false,
  'protocol' => 'imap/notls',
  'port' => 143,
  'folders' => 'INBOX.',
  'namespace' => '',
  'maildomain' => '',
  'smtphost' => 'localhost',
  'smtpport' => 25,
  'realm' => '',
  'preferred' => '',
  'dotfiles' => false,
  'hierarchies' => array()
);

PHP is setup with a 128M memory limit, and imp is setup with a 64M limit.

Everything seems to work fine for a while, then some new mail will come 
in and just screw it up until I fix it with something else.  Any help 
correcting this is appreciated.