Leslie,
Did you delete Adobe reader when you installed Acrobat, as I did? It seems, at least in my case, that AC likes having it around somehow. I uninstalled Adobe Acrobat 9 (the one I bought), ran a repair utility with the uninstaller on Adobe Reader 8, then reinstalled Acrobat.
Now, AC opens PDF's for viewing as before and if I right-click on "open with default program" if opens the PDF in Acrobat.
