Whats this help for dialog

[GrahamL]

Hi
I have designed a dialog in QtDesigner and added a 'Whats this' string for one of the buttons on the dialog.
When I use the preview function in designer the whats this help works perfectly, however when I use the dialog in my application the 'whats this' does not work - the button executes the code for its clicked slot.

How can I get this to work?

I am using Qt 5.0.2
When I press the '?' on the dialog an event of type ToolTip is generated, whereas I thought this should be EnterWhatsThisMode

This used to work under Qt4 so something has changed but I cannot find it

thanks