I' used the latest 2.3.15 BETA 32bit build, Stock WTV and Stock WTV Unprocessed profiles and it's working just fine. I can play back the video in WMP and MCE (with KB2670838 installed). I've uploaded the file in a folder in your sub directory, download it and see if it plays back your MCE and Extender.
Then try to download the latest 2.3.15 BETA, use the stock WTV profiles and compare it.
Then try to download the latest 2.3.15 BETA, use the stock WTV profiles and compare it.