Do you have PHP5 Extensions installed with Sessions enabled? The specific config is in httpd-ssl.conf
Code:
# Inter-Process Session Cache:
# Configure the SSL Session Cache: First the mechanism
# to use and second the expiring timeout (in seconds).
#SSLSessionCache dbm:/var/run/ssl_scache
SSLSessionCache shmcb:/var/run/ssl_scache(512000)
SSLSessionCacheTimeout 300