Starting with eclipse 3.6 SR2 (also affects 3.7) the selection event for graphical editparts is not being received by the editor, so the property sheet is not displayed. I'm guessing, but this might be caused by a bug fix in eclipse jface (or swt?) that removed an extra event notification somewhere.

Workaround is to select a different view, then select the Property view again, but this is not really usable.