The most common reason fo this problem is that some necessary codecs can’t be detected. To solve this you need to upgrade your codec pack. We recommend installing K-Lite Codec Pack. This is a free collection of codecs and related tools for playing all popular media formats. The latest version can be downloaded from
http://www.free-codecs.com/download/K_Lite_Codec_Pack.htm .
You can also get more links on free codec packs from Google.
