Hm, no, I have been creating one MPEG2 file, including sound...
I guess that is the problem? I thought as long as I only have one audio track, it wouldn't matter.
That is not the case, I presume?
I will try with two separate files, thank you for your help!
In the meantime, I found new problems with Encore... 
My PC jumps straight into the DVD menu, but does not play the lead-in-trailer (in preview in Encore it works)..
I know this is a different subject, but maybe you know a quick answer to this as well!
Thanks, John!