[imp] imp-3.2.3 folders problem

[essyug]

Hello,

   I'm using horde-2.2.4 and imp-3.2.3 with a very basic configuration. 
But when I click on the "Folders" link in the top menu of imp, apache2 
hangs up. My imp/config/servers.php is the following (and my 'folders' 
=> 'imapmail/' should be ok, since I've a directory /home/user/imapmail 
for each user):

$servers['imap'] = array(
     'name' => 'IMAP Server',
     'server' => 'localhost',
     'protocol' => 'imap/notls',
     'port' => 143,
     'folders' => 'imapmail/',
     'namespace' => '',
// Of course set to my real domain name
     'maildomain' => 'domain.com',
     'smtphost' => 'localhost',
     'realm' => '',
     'preferred' => ''
);

Please, help me !