iPad: problems with table rows in popovercontrol

Question

I have an iPad application which implements the UISplitViewController. As usual I'm using the popover button to show the root view when the device is in portrait mode. It's seems to be ok at time of launch, but if I turn the device to landscape, then back to portrait, the table in the popover, will have an additional blank row at top, so that I have to scroll down to see the others... Where am I doing wrong?