I get the following message when trying to run the download assistant:
The application cannot be installed due to a certificate problem. The certificate does not match the installed application certificate, does not support application upgrades, or is invalid. Please contact the application author.
From where are you downloading the Adobe Application Manager? Has it been this one
What version of Premiere Elements Mac are you running on your Mac Pro OS Lion 10.7.5? Or, is it that program that you are trying to install with the Adobe Application Manager?