Try this to duplicate the possible bug:

1. Drag a tablelayoutpanel on a form inside the VS 2005 IDE.
2. Make it two rows and two columns.
3. Put a textbox in the seond column on the seond row
4. Set the textbox's columnspan = 2.

Since the default grow behavior of the tablelayoutpanel is to add rows, our
textbox will now move to the newly-added row to occupy two columns.
Everything is fine, right? But wait, we cannot drag our textbox to anywhere
any more. No matter how hard you try, the textbox will stay in the
newly-added row.  This behavior seems not right to me. Is this by design?
Could you please check this out, Martin?

Alan