Try 2 backslashes: \\DVR-SERVER\MEDIA\DVR\
(Or substitute DVR-SERVER with your server's IP address.)
Addendum: You can also try browsing through the Network top-level listing in Explorer. Also, make sure the computer you are browsing from has your local network set as a private network, rather than public, and that Network and Sharing is enabled. (I've never been able to figure out why Windows has certain settings as defaults, or why they change randomly.)

