While playing on the Xbox 360 some wmv video files from the TwonkyMedia server running on a My Book World Edition, I encountered the error 69-C00D36C4.
Since some files did work and some did not I investigated the differences and I can share here a solution: if the wmv files have metadata, the TwonkyMedia server will use the title to list the files, but since the file are accessed as URL, it will need to URI encode them to comply with URI syntax.
The catch is that if the server encode properly space as %20, it does not convert colon(: %3A), but it should, colon is a valid character in a URI, but as a special meaning, and therefore should be encoded when part of a URI component.
Some (lots of) client will ignore the problem, the Xbox does not and will not allow the file to play.
The solution is simple: don't use colon in the title field of your wmv metadata (it might also apply to other kind of files) until TwonkyMedia server is fixed.
Please note that I personally had the problem with colon but it might not be the only problematic character.
If you need to edit your existing metadata, Windows Media Encoder 9 as an editor. I know of no solution for Mac yet.