Alex:
The issue is with the Plasma screen, not the BeoSystem 3. A technology called HDCP (HD content protection) is starting to be used by manufacturers and film studios. It essentially requires that all components in your system can talk to each other to assure that everything is an 'approved' component and not anything which would allow you to copy the DVD.
You'll need to change the Plasma panel, or you're going to run into this problem a lot with HD...
I think Alex is right. Although you have a DVI socket (like the BV7-32), the BV7 required a HD upgrade to support HDCP. If your TV doesn't support HDCP, you'll hear audio but not receive a video signal. ie. it will be blocked. Some TVs show fuzziness, others show nothing at all.
I am quite certain that my plasma does not have HDCP. With this I need to get in contact with the screen manufacturer. I am currently unwilling to invest on a new screen because of lack of HD sources. My test during the weekend seems to be a failure so farπ.
BTW The local DVD rental agencies have a VERY limited offering (both in BD and HD DVDs). This might lead to postponing the whole HD project.