Problem with shared folder after migrating from 2.3,16 to 2.4.10

[Vittorio Manfredini]

I have some problem with shared folder after migrating from 2.3,16 to 2.4.10.

The shared folder are present I can see it with different client, but  
when I try to access nothing happen,
and with horde4 I see in the log the following message :

Sep  1 12:48:10 www HORDE: [imp] PHP ERROR: Trying to get property of  
non-object [pid 19909 on line 353 of  
"/srv/www/htdocs/horde4/imp/lib/Imap.php"]
Sep  1 12:48:10 www HORDE: [imp] IMAP error: Mailbox does not exist  
[pid 19909 on line 340 of "/srv/www/htdocs/horde4/imp/lib/Imap.php"]

the same happen with evolution and thunderbird I can see the folders,  
but I cannot access it and I cannot subscribe to it.

With thunderbird I receive the message that the mailbox did not exists.

I test the namespace using the telnet command this is the result :

 NAMESPACE
* NAMESPACE (("" "/")) (("user/" "/")) (("shared/" "/"))
 OK Completed

The created shared folder was :

shared/folder at example.com

and the result of lam command is :

localhost> lam shared/folder at example.com
admin lkxtecda
user at example.com lrswipkxtecda
cyrus lkxtecda

What I doing wrong ??

Is this a impad configuration problem ?

With the older release I did not have any problem with the same client  
configuration (horde4 and evolution).
-- 
Vittorio Manfredini
email: vittorio at vitsoft.bz