So - ich habe es mittlerweile selbst herausgefunden. Im Adobe-Forum findet sich folgender Eintrag, der ganz einfach eins sagt: Ab in den Benutzer.Ordner, in die Preferences, dort in den Ordner von OPERA (!) und von dort die Datei download.dat entfernen. Das war es!
Es ist bescheuert - aber es funktioniert!
Ok, I had 5 minutes to look into this today. And I found the following:
Under unix, I know a VERY useful utility called truss, that tells you what an application does on a system: IO, etc. So first I searched for the Mac equivalent. It's the ktrace/kdump programs. With that, I found, by launching AHC from the command line, that it bombed out after accessing a file download.dat (well, it's a bit more complicated because kdump shows filename in /.vol file system, youhave to map to your directory and file the file). It turns out that the so called file is located in Opera Preferences. Yes, Adobe uses Opera's outstanding rendering engine for GoLive, and then for AHC I now discovered (it makes sense).
Yes, Opera is indeed my favourite browser, and yes I use it, and yes the download.dat file is the preference file that contains my latest download. It is the name of a file in the download.dat file that would not allow AHC to load. I simply removed the download.dat file and it works again.
(This story is for Adobe Support, in case they would have time to correct this. The offending file name had a lot of dash in its name and was very long.)