who where wrote in
> Now if I click on a link in an email message, FF opens a new blank
> page. So something got broken, but I have no idea what.
Try unsetting, then resetting, FireFox as default browser. If that fails to
fix it, look in Regedit to see if the string "URL Protocol" appears in a few
places, usually associated with a classid (long bracketed string of
hexadecimal digits with a few dashes in it). If you see nothing to match that
simple description before the search reports no further matches for "URL
Protocol" it means you might need some more detailed fix. Reinstalling may be
easier for you than finding it, if there is no direct way to undo the
registry cleaner's action.