Thanks for the quick response.
I have tried it right away, but it did not work.
I created an extra details section, so I got Da and Db.
Then I made sure I had just one subreport per detail section.
Sofar everything was fine, but once I selected "Hide (drill down ok)".
Not only my details were gone, but also my shared variable values.
Searching the net I found another suggestion:
Make the subreport suppress all sections, which works fine.
And then set "Suppress Blank Section" in the main report.
But that does not supress the sections so I endup with a lot of blank lines. Don't know why, it works with other sections, but not here ...
Still searching for a solution.
IP Logged
Although I'm not sure that's there real reason.
I still don't know what precisely caused this. 
The only thing I could do was go back to a prior version (I do make a lot of back-ups under these circumstances 
