Maybe the reason is that you once copied DLLs from old versions (A7) like Pappenheimer suggested, because a mix of old and new DLLs will probably make a mess of your import filters. Deinstalling wont help then because it only deinstalls A8 but does not erase those old versions. My advice is to deinstall first all Gamestudio versions completely and then manually erase the folders from the hard disk, especially the MED plugins folder, then install A8 again.