Whatever their reasons might be, a couple of GOP contenders missed the deadline. Rick Santorum, Michele Bachmann, and Jon Huntsman will not have their names appear on the ballot.

http://www.huffingtonpost.com/2011/12/23/virginia-ballot-michele-bachmann-rick-santorum-jon-huntsman_n_1167524.html

According Quinnipiac's latest poll (12/13 - 12/19), neither of those candidates are poised to take Virginia anyway:

Gingrich 30%
Romney 25%
Paul 9%
Perry 6%
Bachmann 6%
Huntsman 4%
Santorum 3%

http://www.realclearpolitics.com/epolls/2012/president/va/virginia_republican_presidential_primary-1776.html