This seems to me like a bug to me.
It works for me in CS4 and CS5.5, but it doesn't in CS5.
So, we can conclude that this is some really
bad bug which was "introduced" in CS5 and fixed in CS5.5.
Thanks Marijan, for testing and letting me know!
I filed a bug report now. We would perhaps have to "force" a couple of our clients to an upgrade from CS5 to CS5.5 in order to beat this bug and get it working, unless Adobe acknowledges it quickly, which I don't count on.
No good news then... I took for granted that the interface would work in CS5 if I made it in CS4.
(The thing that I was mostly concerned about was a tree view which I tested in Mac/PC and on CS4/CS5. Not the "tabbed panel"...)
Adding this answer I got from Adobe:
Monday, November 21, 2011 2:21:03 AM PST
I was able to replicate this problem with InDesign CS5. This bug seems
to have already been fixed as a side effect of some code change within
I have logged this under bug # 3050997. This will now be worked upon by
InDesign engineering and should be fixed soon.
I'll keep you informed about updates on this bug.
Message was edited by: Andreas Jansson. Response from Adobe added.
Great, I will implement this workaround unless Adobe releases their bug fix soon!
I got a mail three weeks ago, where they told me that a so called MA (Master Archive) patch will be released within about one month, and that this bug will be solved in that "MA".
But it's really a great little workaround you've found out. (I just wish it had been found last autumn, or that the Adobe technicians could have known about and sent me this tip at the time I reported the bug :-)