First, I found this link which tells you how to keep up to date with qt-copy: just download the correct snapshot from the troll's ftp site.
I downloaded the 10/02 snapshot and applied the latest msvc 2005 patches from the qtwin sourceforge project. Then I configured and built qt. Everything went fine.
Now back to building qtdbus. As mentioned in the kdelibs.com tutorial, I checked out qdbus from qt-copy in the kde svn and replaced the qdbus dir in the qt package. The problem is that DBUSDIR is not recognized any more in the build. So I opened qdbus/src/src.pro in my editor, and put in a few lines I found in an earlier version of that file in the subversion repository.
My win32 part of src.pro now reads:
+ INCLUDEPATH += $$(DBUSDIR)
+ LIBS+= -L$$(DBUSDIR)/lib
LIBS += -lws2_32 -ladvapi32 -lnetapi32
Then I started qmake -spec win32-msvc2005 -recursive and the build started. But there was yet another problem. The link of qdbus.exe missed the xml library. So I added
QT = core xml
Another nmake and everything builds fine. Let's see what's next...