Tente instalar o QT-SDK a partir do link . Acabei de fazer no Ubuntu 12.04.
recebendo o seguinte erro ao instalar o criador qt através do centro de software.
The following packages have unmet dependencies:
qtcreator: Depends: libqt4-help (>= 4:4.7.1) but 4:4.8.1-0ubuntu4 is to be installed
Depends: libc6 (>= 2.15) but 2.15-0ubuntu10.2 is to be installed
Depends: libgcc1 (>= 1:4.1.1) but 1:4.6.3-1ubuntu5 is to be installed
Depends: libqt4-declarative (>= 4:4.7.4) but 4:4.8.1-0ubuntu4.2 is to be installed
Depends: libqt4-designer (>= 4:4.7.1) but 4:4.8.1-0ubuntu4 is to be installed
Depends: libqt4-network (>= 4:4.7.1) but 4:4.8.1-0ubuntu4.2 is to be installed
Depends: libqt4-script (>= 4:4.7.1) but 4:4.8.1-0ubuntu4.2 is to be installed
Depends: libqt4-sql (>= 4:4.7.1) but 4:4.8.1-0ubuntu4.2 is to be installed
Depends: libqt4-svg (>= 4:4.7.1) but 4:4.8.1-0ubuntu4.2 is to be installed
Depends: libqt4-xml (>= 4:4.7.1) but 4:4.8.1-0ubuntu4.2 is to be installed
Depends: libqtcore4 (>= 4:4.8.0) but 4:4.8.1-0ubuntu4.2 is to be installed
Depends: libqtgui4 (>= 4:4.8.0) but 4:4.8.1-0ubuntu4.2 is to be installed
Depends: libstdc++6 (>= 4.4.0) but 4.6.3-1ubuntu5 is to be installed