Lion fails to use new dns

Several days ago, I changed hosting for my sites. The new DNS propagated rapidly and the old hosting was cancelled. My other three MACs and Windows machines access the new server, but one of my iMACs still tried to access the former server. I have cleared the browser histories, and even download Camino. When I try to access my sites, I get a page from the old host saying that the site is no longer available.

Why does Lion seem to think that my old host is the default for my sites, when all other machines have no problem whatsoever? Where in Lion is this information buried? It is consistent across different browsers, but only on this one iMAC.