Complex sentence: The 2005 event received corporate sponsorship from Solo Mobile, which also sponsored the 2006 festival and intended to do likewise in 2007 and 2008, but in early June 2007 before the full band lineup had been announced, all mention of Solo disappeared.
Split into simpler sentences: The 2005 event received corporate sponsorship from Solo Mobile, which also sponsored the 2006 festival. Originally slated to sponsor in 2007 and 2008, but in early June 2007 before the full band lineup had been announced, all mention of Solo disappeared.