Bug Fixes in Development Tools
It looks as though the bug fixed by commit 644749 may have been causing the problems with the advanced code generators, too.
I'm experimentally lifting the BUG84739 barrier.
If you feel adventurous and want to help improving Umbrello then go to the Setting->Configure Umbrello menu and enable "Use new C++/Java/Ruby generators".
Is the advanced-codegen configuration back to stable? Please send reports <a href="http://bugs.kde.org/show_bug.cgi?id=84739">here</a>.