Did you ever let a site expire and lay dormant for a while? Then come back to it later, to set up a new site on the domain name? If you have, you may have noticed that those types of sites, stay dormant within the SERPs even longer then what you may have expected.
A thread at Cre8asite Forums named Google Cache Other Website, Instead Of Mine tells the story of just that. Webmaster lets site expire, then puts new site up at the domain name, but the cache of the site still has the old version. Apparently, the spiders have not revisited the site in a while.
Search engines have a repository of expired domain names. Or at least I was inferred this information by a search engine representative. If a domain expires, it goes into that bucket and is checked less often for any update. Of course we know about sites that are not updated often, are spidered less frequently. Same with expired sites. So give the site more content, give the site more links and give the site more time and it will be revived in the search engines again.