PopUpX no longer works properly wit the current release of OS-X, and given the rumors
that proper popup windows will be available in the next OS X release, it isn't worth
the time to update it.
A technique that I have found useful to simulate popups is to set the dock to be on the right
edge of the screen (vertically oriented) and put folders into it; click and hold to pop up a
menu of the contents. You can make this much more effective by customizing the folder icons
so they look distinctive. I use the "Can Combine Icons" app to actually add a small text label
to the icon so I can tell what folder is what without mousing over it (I bribed the author
to add the text stamping feature)