I have been using MS 4.0 & DVD Architect 2.0 for a while and I decided to get the updates not that I'm done with the annual Christmas project.  
When ugrading DVD Architect 2.0 (build 22) to 2.0b a new program group was created and when I attempt to start it up the serial # is prompted for again.  The one that came with DVD Architect 2.0 (build 22) does not work for some reason.  
I found the link to the upgrade on an eariler post last week some time.
Is anyone else having the same problem?