I did a system restore to an earlier date and then undid it again. FF now does not work. I have uninstalled Firefox and ZASP (cpes_cleaner does not seem to work with windows 7 x64, even though it starts and run/cancel are shown, once I click run it disappears) and reinstalled them to no avail. The FF add-on is shown as installed and the toolbar appears under view>toolbars as well but actually they don't work, no toolbar in the browser window and downloads do not pass by FF any more.
I have also used the FF uninstaller to uninstall it, that worked (no add-ons or ZA toolbar anymore), but the standalone installer even though it worked as well, except the problem was not solved. Back to square one.
Windows 7 Pro x64