Can't change background color of QDoubleSpinBox in Linux

The following code works fine in Windows XP to switch the background color of a QDoubleSpinBox between blue and the defult value:
On Linux (Ubuntu 9.10 and several earlier Ubuntu releases it doesn't work).

template<> void selectScanWidget(QDoubleSpinBox* w, const std::string&, bool bScan)
{
if(bScan)

{ palInitial = w->palette(); palScanning.setColor(QPalette::Base, QColor(150, 170, 255)); //light-blue }

w->setPalette(bScan ? palScanning : palInitial);
}