Wiki whitelist reverts on each reboot

I want to be able to include a DuckDuckGo search field as an iFrame on a Wiki page, using Server 3.1.1 on Mavericks 10.9.2. As you all know, only Youtube and Vimeo sites are allowed by default.

So I edit whitelist.plist to include the following:

<key>iframe_sources</key>
     <array>
          <string>youtube.com</string>
          <string>vimeo.com</string>
          <string>duckduckgo.com</string>
                </array>

So far so good. Only this doesn't really work. So I figure "I should probably reboot to load the settings", but when I check whitelist.plist after rebooting, the file has reverted to the original content.

And yes; I use "sudo". And yes, I save changes. I've double checked by opening the whitelist again before rebooting, and the extra line is present before reboot.

So the question is: How can I edit the whitelist and keep the changes (not to mention get it working)? Is there an additional location? Do I need to disable some kind of "protect my configuration" setting?

From the log:

Mar 27 13:18:15 OSXtest.local SubmitDiagInfo[562]: 
Failed to load serverside whitelist, using cached list: Error Domain=NSURLErrorDomain Code=-1001 "The request timed out." 
UserInfo=0x7ff802c392a0 {NSUnderlyingError=0x7ff802c0b3d0 "The request timed out.", 
NSErrorFailingURLStringKey=https://radarsubmissions.apple.com/macSubmissions/diagnosticwhitelist.jsp?osv=10.9.2, 
NSErrorFailingURLKey=https://radarsubmissions.apple.com/macSubmissions/diagnosticwhitelist.jsp?osv=10.9.2, 
NSLocalizedDescription=The request timed out.}

+H+