IMP3: problem when displaying folder list

[Stefan Katzenbeisser]

Dear all,

I recently upgraded my IMP installation from imp-2.2.7 to
imp-3.0. Unfortunately, there seems to be some problem in the file
folders.php. When I click on "Folders", I get the following error
messages:

Warning: Undefined index: attributes in /home/morpheus/www/horde/imp/lib/Tree.php on line 689

Warning: Undefined index: next in /home/morpheus/www/horde/imp/lib/Tree.php on line 653

Warning: Undefined index: level in /home/morpheus/www/horde/imp/lib/Tree.php on line 654

Warning: Cannot add header information - headers already sent by (output started at /home/morpheus/www/horde/imp/lib/Tree.php:689) in /usr/local/lib/php/HTTP/Compress.php
on line 75

Warning: Cannot add header information - headers already sent by (output started at /home/morpheus/www/horde/imp/lib/Tree.php:689) in /usr/local/lib/php/HTTP/Compress.php
on line 76

Warning: Cannot add header information - headers already sent by (output started at /home/morpheus/www/horde/imp/lib/Tree.php:689) in /usr/local/lib/php/HTTP/Compress.php
on line 86

Warning: Cannot add header information - headers already sent by (output started at /home/morpheus/www/horde/imp/lib/Tree.php:689) in /usr/local/lib/php/HTTP/Compress.php
on line 100

followed by some crap. However, if I press the reload button of my web
browser, the folder list gets displayed properly.

Although a similar problem was reported on this list some months ago,
I could not find a solution. Currently I still use the "IMAP2bis Service 7.8(100)"
IMAP server [yes, I know that this server is quite old and needs to be updated
very soon ;-)] and the following servers.php file:

$servers['imap'] = array(
    'name' => 'IMAP Server',
    'server' => 'mail.netkey.at',
    'protocol' => 'imap',
    'port' => 143,
    'folders' => '',
    'namespace' => '',
    'maildomain' => 'netkey.at',
    'smtphost' => 'mail.netkey.at',
    'realm' => 'mail.netkey.at',
    'preferred' => ''
); 

I run Apache 1.3.22 and PHP 4.1.0.

Does anyone have a similar problem?

Thanks for your help!
Stefan