Hi serhan,
The WMP client happens to do a pre-roll of the content by default, meaning that it will download the entire file and then do the seeks locally on the client. In v2.0, we made a change to send the request header 'Accept-Ranges: bytes' which should tell the client not to do this. Instead, the client should send byte-range requests for subsequent seek requests. Though, I'm not sure whether the client will end the current download or continue to download since the pre-roll happens concurrently.
One thing I would suggest is to download Fiddler from http://www.fiddler2.com/fiddler2/ to trace the http traffic between the server and your client machine. It's a 3rd party tool so I can't offer much support for it. It should work either from the client or server machine, though sometimes it depends on the client you are using.
When you have it installed, you should be able to verify whether or not the 'Accept-Ranges' header is being sent for entries where 'canSeek = true' and that it is not sent when 'canSeek=false'. You can probably also verify the timing of the requests from the client to see if a pre-roll is indeed happening.
If you're still seeing issues, feel free to post your traces and I'll see if I can help to debug what is happening. thx...
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