Dialog block in windows

In linux everything works, in windows not.
I am wondering if Qt is a real cross-platform library...
Anyway, I have the following code:

Code:

---

void MyPlot::gridset()
{
	gridSettings->setVisible(true);
	gridSettings->raise();
}

---

which is callad after a context menu action. In linux I get the dialog gridSettings (created by the designer), and I can user its controls and I can close it.
In windows, it appears, blocks, and stary there forever....

Could you attach the .ui file? Perhaps some modality property was messed up.