http://www.pollster.com/08-VA-Pres-GE-Mv O.php
Virginia is competitive. With the combined forces of Mark Warner, Webb, and Kaine, VA is a prime pick-up opportunity. As was pointed out, even a loss in VA, if it means the GOP is spending money defending a "safe" state, opens up other poaching opportunities.
The south is (and will be for the foreseeable future) GOP country. The only state that changes with Clinton on the ticket is Arkansas--but she easily loses in VA to McCain in that scenario.