Hi,

Have a look at Qt-4.8.0/src/3rdparty/webkit/Source/WebKit/qt/QtWebKit.pro where libWebKitSystemInterfaceLion.a is forced even if you specify MACOSX_DEPLOYMENT_TARGET to an older OS version. This causes the missing symbol on older systems.

I edited the .pro by hand to use libWebKitSystemInterfaceLeopard.a but a bug should probably be logged.