I have just setup a new server farm for SharePoint. After finish installation for all server farm, I start configuring the Shared Service Provider, include activating SharePoint Search. Once the Search turned on, the whole SharePoint site is inaccessible from the server that hosts the Central Administration, all other Web Front End is ok. The page just displayed 503 - Service unavailable. IIS showed that Application Pool has been stopped, so I start it again, but everytime there is a request to the site, the Application Pool stop again.
After checking through the forum and all blogs, it turns out the evil here is the IPv6 is enabled. After turn IPv6 off, all the site work properly again. Damn.. wasted almost 1 hour close to midnight..