Would you be able to send us photos of the plant so we can take a look at the symptoms you are seeing? Are the dying branches at the top of the plant or the bottom? Are the leaves dropping off of the plant or do the branches retain the dead leaves? We would be happy to help, but we need more information. You can attach up to three photos to this reply.
Whole branch turns brown and dies at once, from top to base. Leaves do not drop off. When I remove a branch, it is brown and dead from tip to base.
ics were taken under flashlight illumination. I can get better shots in daylight tomorrow.
We viewed your photos. This looks like volutella, a fungal disease on the boxwoods. Dense foliage encourages fungal diseases such as volutella stem blight or canker. Usually this can be solved through cultural methods such as pruning and thinning. The plants should be thinned to improve good air circulation and light penetration. Shake out and remove all old leaves that remain in the branch crotches and from around the base of the plants. See our website for more information and the pruning video at the bottom of the page. http://extension.umd.edu/hgic/volutella-blight-boxwood
Monitor the shrub and wait for new growth in the spring to thin, prune, and remove any fallen leaves. You will also be able to assess any winter damage.