x11-libs/qt-4.3.1-r1 installs the documentation to /usr/share/doc/qt-4.3.1-r1/.
But Assistant is looking for these files in /usr/share/doc/qt-4.3.1/. So i always get errors the documentation could not be found.
Sorry,that's NOT a bug, just my fault :)
I had to remove ~/.config/Trolltech/Assistant.conf, and all docs are found.
Thanks for reporting back. :)