I aint 100% sure but in the past when i have had similar problems it is or has been down to corrupt codecs i get the download of codec from here
http://www.codecguide.com/download_k-lite_codec_pack_mega.htm and that in the past as resolved my problem..yours may be totally unrelated but they are worth having anyhow
Just a thought have you tried unistalling the dvd in device manager and then restarting, windows will then load the generic drivers for the dvd it worth a go just in case you got bad drivers