QComboBox shows its drop down in the wrong place on 4.6.3

In Qt 4.6.1 and 4.6.2 a QComboBox would show its drop down list directly underneath the combobox control and it would respect (almost) the visible items set with setMaxVisibleItems().

In 4.6.3 the "drop down" list is now shown at the bottom of the screen, directly above the softkeys. Also, it seems to take no notice of setMaxVisibleItems. Please see attached image for comparison.

Is this an intended change to QComboBox, and if so is there any way to get the old behaviour?

Code to reproduce:

QComboBox* cb = new QComboBox( this );
cb->addItem( "abc" );
cb->addItem( "def" );
cb->addItem( "ghi" );
cb->addItem( "jkl" );
cb->addItem( "mno" );
cb->addItem( "pqr" );
cb->addItem( "stu" );
cb->addItem( "vwx" );
cb->addItem( "yz1" );
cb->addItem( "234" );

cb->setMaxVisibleItems( 3 );