shm (warnings)

[nsolano@cima.tij.uabc.mx]

I'm using IMP 2.2.4 with horde 1.2-4 horde-shm package. but i´m receiveing the 
above message very frequently.
 any guess what I´m missing?

 Warning: not enough shared memory left in /var/www/horde-phplib/ct_shm.inc on 
line 54
 
 Warning: Cannot add header information - headers already sent by (output 
started at /var/www/horde-phplib/ct_shm.inc:54 ) in /var/www/horde-
phplib/session.inc on line 120

Warning: variable key 99 doesn't exist in /var/www/horde-phplib/ct_shm.inc on 
line 79


Thanks.