Ok solved, probably it's related to the high number of mail folder of 
that users, and the php memory_limit parameter.

Changed it , restarted apache everithing is ok now.

I've found something in the apache error log:

a user that works fine has this entry:

[error] PHP Fatal error:  Allowed memory size of 8388608 bytes 
exhausted (tried to allocate 54564 bytes) in Unknown on line 0



a user with the sidebar that doesn't appear has this entry:

[error] PHP Fatal error:  Allowed memory size of 8388608 bytes 
exhausted (tried to allocate 42495 bytes) in 
/var/local/www/webmail/horde/lib/Horde/Tree/javascript.php on line 140





ale

I've Horde framework installed authenticating against cyrus via IMP.

Everithing works fine except that for some users that sidebar doesn't 
appear; no error appears in the log file (even with debug_all) and no 
javascript error in the browser.



Any idea of what could be?



Many thanks....

Ale