I have seen that some people have issues with Lion, Pages and Endnote and that there are some work-arounds.
My problem is different:
The citation option is not appearing in my insert menu in Pages
Maybe people here are upgrading from snow leopard to Lion and keeping the original Endnote and Pages installations and that is why it works (sort of) for them.
Mine is a fresh new Mac with Lion installed but no previous installation of Endnote or Pages or Word as I did not use the migration software.
I have new copies of Endnote X4, Pages 09 4.1, and Word 2011 installed but Endnote it is only working in Word