Thanks for the answer
PHP.ini is on the server I am using. I can only spécify some variables.
I can't change error reporting parameter.
On the same server I have 2 other masters sites with a lot of slaves sites and these run well. Then I think that PHP parameters are well configured.
I have modified the file "admin.multisites.php" and added the line :
error_reporting( JFactory::getApplication()->getCfg('error_reporting') & ~E_STRICT);
but nothing have changed
I can try with the 1.3 last version
but can I update from 1.2 directly with extension manager without risk for the slaves site ?