No, a configured WORKGROUP is necessary for the WDTV to “discover” the PCs that are sharing media.
Now, that does NOT apply if you’re using “Media Servers” as opposed to “Network Shares.” DLNA (Media Server) has no dependency on Workgroup configuration. That’s one reason some people prefer them.
What will monkey with the stability of a Network Share is if something happens in your network while watching a move, that forces a “Re-election” of a master browser.
In other words, if you’re watching a movie, and some other device in the WORKGROUP comes up (or goes down) and forces a Windows Networking recalculation, it’s possible the WDTV will get hosed.
Check in your Synology to see if there’s a setting called “Master Browser.”
There is on my Q-NAP, and I have it enabled. What that does is force that device to win the election every time. And since my NAS is powered on 24x7, it never has these issues. 
If you really want to dig into the nuts and bolts, you can run the test I highlight below (from a script.)
Run it BEFORE you start a movie, then run it IMMEDIATELY after it “Breaks,” and see if anything changes.
In other words, if your Master Browser is “X” before, and becomes “Y” when it breaks, then that could very well be the issue.
This is how to find possible problems with the Master Browser on your network, which will affect when and what servers appear on your WDTV Network Shares.
On one of your PCs, open up a “Command” window.
(In Win Vista and Win7, click the Orb, and in the search box, type CMD. An icon will appear above the box that says cmd.exe. Click it, and a Command window will open.)
(In WinXP, Click START, then RUN…, and in the box, type CMD. A Command Window will open.)
In the command window, enter the command “net view,” like this:
…
…
C:\Users\Tony>net view
Server Name Remark
\BIGNAS1 Big Freakin’ NAS Server 1
\MARS
\NEPTUNE
\WDTVLIVE WDTV LIVE
The command completed successfully.
In my example, there are four active devices that Windows has discovered.
Now, for EACH of those, issue the command “nbtstat -a (name)” for example:
C:\Users\Tony>nbtstat -a bignas1
Local Area Connection:
Node IpAddress: [10.0.0.157] Scope Id:
NetBIOS Remote Machine Name Table
Name Type Status
BIGNAS1 <00> UNIQUE Registered
BIGNAS1 <03> UNIQUE Registered
BIGNAS1 <20> UNIQUE Registered
…__MSBROWSE__.<01> GROUP Registered
WORKGROUP <1D> UNIQUE Registered
WORKGROUP <1E> GROUP Registered
WORKGROUP <00> GROUP Registered
…
So, we got lucky here, the FIRST system, BIGNAS1, indicates that it is the master browser, since it lists the name …__MSBROWSE__.
You need to find out WHICH system is your master browser. If none of these steps work as described, then the issue is likely on your PC itself, and that will require substantial additional troubleshooting.
