From the list of effected boxwoods, it looks like all boxwoods have a chance of getting blight. The list includes japonica, microphylla, sempervirens and sincica.
Here's a link to the Conn Ag Station report.
Initial Symptoms - dark lesions on leaves followed by defoliation. Then, dark cankers appear on the stems.
|Tsubo-en Zen-garden diary|
A fungicide spray is recommended for prevention, not cure. Recommended fungicides include chlorothalonil and mancozeb.
Take a look at the photos on the link to the original article and then go check your boxwoods.
Also, go to Piet M Patings blog (link below box blight photo on left) where he talks about blight in his Zen garden. This is a gorgeous and inspiring website.
You will find a lot of good information about box at that link!