the bundled one didn't work...
on the last log there was a problem where libsmtrp was not activated. I recompiled ffmpeg with it, and got the warning gone (attaching the new log), but it still does not work.
ONly thing I can think off, is reinstalling the app, using the ffmpeg bundled, and sending you the logs, see if that can help.

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new log:
2012-05-24 01:31:31,748 INFO [WebServer] Socket buffer set to 65535 bytes
2012-05-24 01:31:31,749 INFO [Device] Created UPnP Device with UUID: 07f90c8c-4545-38b0-b145-074673426582, bound address: 192.168.1.129
2012-05-24 01:31:31,852 INFO [PluginCompilerThread] Looking for plugins at /Applications/Serviio/Serviio.app/Contents/Resources/Java/plugins
2012-05-24 01:31:31,852 INFO [PluginCompilerThread] Started looking for plugins
2012-05-24 01:31:32,272 INFO [AbstractTranscodingDeliveryEngine] Cleaning transcode engine and its data
2012-05-24 01:31:32,458 INFO [WebServer] WebServer starting on port 8895
2012-05-24 01:31:32,473 INFO [EventSubscriptionExpirationChecker] Starting EventSubscriptionExpirationChecker
2012-05-24 01:31:32,473 INFO [EventDispatcher] Starting EventDispatcher
2012-05-24 01:31:32,473 INFO [DiscoveryAdvertisementNotifier] Starting DiscoveryAdvertisementNotifier
2012-05-24 01:31:32,506 INFO [RendererSearchSender] Searching for Renderer devices
2012-05-24 01:31:32,506 INFO [RendererExpirationChecker] Starting RendererExpirationChecker
2012-05-24 01:31:32,507 INFO [DiscoverySSDPMessageListener] Starting DiscoverySSDPMessageListener using interface en1 (en1) and address 192.168.1.129, timeout = 0
2012-05-24 01:31:58,574 INFO [FeedUpdaterThread] Started looking for information about online resources
2012-05-24 01:31:58,580 INFO [LibraryAdditionsCheckerThread] Started looking for newly added files
2012-05-24 01:31:58,603 INFO [LibraryUpdatesCheckerThread] Started looking for updates to currently shared files
2012-05-24 01:32:01,884 INFO [ContentDirectoryDefinitionParser] Parsing ContentDirectory definition
2012-05-24 01:32:02,521 INFO [BrowsingCategoriesMessages] Loaded browsing categories message bundle for locale: es