Cron error, server totally out of use

503 r18860
Oracle, in base file storage
jdk 1.6

I have imported the online demo, validated full site
I have imported it a second time
I have defined a site replication from my first site to my second one

-> an exception is raised in console
-> I can access none of my two virtual sites
-> in admin center, I can access only server params tab, as if I had created no site.
-> I cannot access virtual sites management screen