Help with a unknown file format

I have this file I pulled from the “AvatarCache” folder of the storage folder of Microsoft Silverlight. I am not sure about how it is formated or if it is compressed (very likely) and need some help with it. I am a bit of a noob when it comes to cracking file formats, so that is why I am asking for help here. I did notice, however, that it has a header of “YTGR”. I suspect it is a type of model (as that is what is stored in those folders normally) Any ideas?

Here is the file:

A quick google returns this tool:
http://forums.xbox-scene.com/index.php?/topic/746969-velocity-cross-platform-tool-fatx-included/

The tool describes the file as a “YTGR security descriptor”. I don’t think this is a model.