Can't get QT 5.1.1 working on OS X 10.6.8

Can't get QT 5.1.1 working on OS X 10.6.8

System Info
I am running Mac OS X 10.6.8 and I have XCode 3.2.5 installed.
Running which gcc outputs /usr/bin/gcc
What I've Tried
I've tried installing qt using both the offline and online installers:

qt-mac-opensource-1.4.0-2-x86_64-online.dmg
qt-mac-opensource-5.1.1-clang-offline.dmg
However in the middle of Installing component Essential modules, both of
these give me the following errors (no matter how many times I hit Retry):

Error during installation process (qt.511.clang_64.essentials):
Command install_name_tool failed.
Arguments: -change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtQuickTest.framework/Versions/5/QtQuickTest
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtQuickTest.framework/Versions/5/QtQuickTest
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtWidgets.framework/Versions/5/QtWidgets
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtWidgets.framework/Versions/5/QtWidgets
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtGui.framework/Versions/5/QtGui
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtGui.framework/Versions/5/QtGui
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtCore.framework/Versions/5/QtCore
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtCore.framework/Versions/5/QtCore
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtQml.framework/Versions/5/QtQml
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtQml.framework/Versions/5/QtQml
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtNetwork.framework/Versions/5/QtNetwork
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtNetwork.framework/Versions/5/QtNetwork
/usr/local/qt/5.1.1/5.1.1/clang_64/bin/qmltestrunner
Output:
And during Installing component Add-On modules, I get the errors:
Error during installation process (qt.511.clang_64.addons):
Command install_name_tool failed.
Arguments: -change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtQuickTest.framework/Versions/5/QtQuickTest
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtQuickTest.framework/Versions/5/QtQuickTest
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtWidgets.framework/Versions/5/QtWidgets
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtWidgets.framework/Versions/5/QtWidgets
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtGui.framework/Versions/5/QtGui
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtGui.framework/Versions/5/QtGui
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtCore.framework/Versions/5/QtCore
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtCore.framework/Versions/5/QtCore
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtQml.framework/Versions/5/QtQml
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtQml.framework/Versions/5/QtQml
-change
/Users/bld.qt/bamboo-agent-home/xml-data/build-dir/DQTC-LGPLRELEASEBUILD510-OSX106/______________________________PADDING______________________________/lib/QtNetwork.framework/Versions/5/QtNetwork
/usr/local/qt/5.1.1/5.1.1/clang_64/lib/QtNetwork.framework/Versions/5/QtNetwork
/usr/local/qt/5.1.1/5.1.1/clang_64/bin/qmltestrunner
Output:
After hitting Ignore on both, the installation continues fine, but then I
try using Qt Creator and get the following message under Preferences: Qt
version is not properly installed, please run make install

After installation, running which qmake outputs
/usr/local/qt/5.1.1/5.1.1/clang_64/bin/qmake