I don’t have a solution, but I have a workaround. I had the same issue - intermittent connectivity, slow. There’s absolutely nothing wrong with my network, it’s all hard-wired, all the computers (win 7 / Win 8) can browse to each other, play media, etc. The proper computer was filing the role of Master Browser.
For approximately a year, I used a Synology NAS acting as a DLNA “media server”. It worked perfect, never an issue. I took down the NAS and built a dedicated Windows (7) media center, or HTPC. That’s when the trouble started with my WD unit.
To solve it, I stopped using network sharing to get to the media from the WD device and instead downloaded Universal Media Server (installed on the dedicated HTPC), which is free and acts as a media server, the same way the orginal Synology NAS did. Problem solved, easy setup! My WD unit is back to being fast, always finds the media server etc.
I’m convinced there’s something wrong with the unit or the firmware (for some) and WD isn’t interested in solving it.
Although the Master Browser can cause sharing issues, so can improper set up of WDTV. Here is an issue with passwords, etc. that can cause people lot of problems, too. So a few years ago I wrote this tip up and it has helped a lot of people. Review this post and see if you have your WDTV set up either of these ways – correctly. See the beginning comment.