pb with cache_module and disk_cache_module / index.html

Hi,
I am running under FreeBSD 6.1 and Apache2.
If i am loading this two modules, my apache do not want to use the
DirectoryIndex ...
If i comment this two modules, apache2 work properly ....

My config:

DirectoryIndex index.html index-multi.html index.php index.html.var

</IfModule>
<IfModule mod_cache.c>
<IfModule mod_disk_cache.c>
CacheRoot "/var/cache/apache2"
CacheSize 50000
CacheEnable disk /
CacheDirLevels 5
CacheDirLength 3
CacheDefaultExpire 86400
CacheIgnoreCacheControl On
CacheIgnoreHeaders Set-Cookie
CacheMaxExpire 86400
</IfModule>
</IfModule>

Any idea ?

Thx