Conflict with autoload and memcached when restarting Apache

I get some great results for a newsletter with html mail but I have problems of stability on the server.

When I restart Apache on my server, [ VPS ubuntu 9.04 with about 5 websites ] I have a crash of the two bigger web sites [ one under magento, the other under drupal 6.20 with htmlmail and autoload... memcached is running on server and with the module Memcache API and Integration ].

Here you are the "dead" screen messages :

Notice: Use of undefined constant FALSE - assumed 'FALSE' in /.../.../.../htdocs/sites/all/modules/memcache/dmemcache.inc on line 385
Notice: Use of undefined constant FALSE - assumed 'FALSE' in /.../.../.../htdocs/sites/all/modules/memcache/dmemcache.inc on line 252
Notice: Use of undefined constant AUTOLOAD_REGISTRY_RESET_LOOKUP_CACHE - assumed 'AUTOLOAD_REGISTRY_RESET_LOOKUP_CACHE' in /.../.../.../htdocs/sites/all/modules/autoload/autoload.module on line 163
Notice: Use of undefined constant AUTOLOAD_REGISTRY_WRITE_LOOKUP_CACHE - assumed 'AUTOLOAD_REGISTRY_WRITE_LOOKUP_CACHE' in /.../.../.../htdocs/sites/all/modules/autoload/autoload.module on line 171
Notice: Use of undefined constant TRUE - assumed 'TRUE' in /.../.../.../htdocs/includes/database.mysql-common.inc on line 40
Notice: Use of undefined constant DB_QUERY_REGEXP - assumed 'DB_QUERY_REGEXP' in /.../.../.../htdocs/includes/database.mysql-common.inc on line 41
Warning: preg_replace_callback() [function.preg-replace-callback]: Delimiter must not be alphanumeric or backslash in /.../.../.../htdocs/includes/database.mysql-common.inc on line 41
Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in /.../.../.../htdocs/includes/database.mysqli.inc on line 185
Notice: Use of undefined constant FALSE - assumed 'FALSE' in /.../.../.../htdocs/includes/database.mysqli.inc on line 191
Notice: Use of undefined constant TRUE - assumed 'TRUE' in /.../.../.../htdocs/sites/all/modules/autoload/autoload.module on line 194
Warning: require_once(./FALSE) [function.require-once]: failed to open stream: No such file or directory in /.../.../.../htdocs/sites/all/modules/autoload/autoload.module on line 201
Fatal error: require_once() [function.require]: Failed opening required './FALSE' (include_path='.:/usr/share/php:/usr/share/pear') in /.../.../.../htdocs/sites/all/modules/autoload/autoload.module on line 201

If I remove both autoload module folder and htmlmail module folder, then restart apache2, all my website are coming back !

I am not a expert so I can't identify the problem. It looks like a memory problem because the errors messages are not always the same and two virtual hosts are done each time... I tryed a lot of other action like restarting memcache daemon or upgrading php memory... but the only one that solves the problem is to remove html mail and autoload module.

Thanks you in advance for your help