ALERT - canary mismatch on efree() - heap overflow detected

[Frank Bonnet <f.bonnet@esiee.fr>]

Hello

I'm in trouble with such error messages with apache2 + php5 on a Lenny 
5.0.7 server
those php5 modules are installed on the machine :

ii  libapache2-mod-php5               5.2.6.dfsg.1-1+lenny9      
server-side, HTML-embedded scripting language (Apache 2 module
ii  php5                              5.2.6.dfsg.1-1+lenny9      
server-side, HTML-embedded scripting language (metapackage)
ii  php5-cli                          5.2.6.dfsg.1-1+lenny9      
command-line interpreter for the php5 scripting language
ii  php5-common                       5.2.6.dfsg.1-1+lenny9      Common 
files for packages built from the php5 source
ii  php5-gd                           5.2.6.dfsg.1-1+lenny9      GD 
module for php5
ii  php5-ldap                         5.2.6.dfsg.1-1+lenny9      LDAP 
module for php5
ii  php5-mcrypt                       5.2.6.dfsg.1-1+lenny9      MCrypt 
module for php5
ii  php5-sybase                       5.2.6.dfsg.1-1+lenny9      Sybase 
/ MS SQL Server module for php5


Any info , help , tricks welcome !

Thanks