I checked your link Robku, and to me this issue seems like something else when diagnosing with firebug. First time I checked the gallery, it did not seem to load past the first stage ... this is the process where it loads the heaviest item, which is folders:
http://robku.nl/foto/imagevue.php?a=folders
After first try, it seemed to load fine ... If this script does not load, there is something related to the server.
As for any preloader hanging ... I can not see this. I only saw the circular preloader on first load, which basically means its NOT LOADING ... not that the preloader is hanging.
Thereafter, after this script seemed to load well as far as I could see, I didnt see any other problems. The audioplayer did not load here, but that is because the audioplayer makes sure there is enough bandwidth to stream BOTH audio files AND images. In the case where it takes a long time to preload, the program thinks the connection is slow, and will disable the audio player. You can change this by going to admin -> settings -> audioplayer.minimum_connection ... lower the value to as low as 0, but then you may have users on low speed modems that are attempting to play audio and images (which will seem very slow for them).
As for the general issue in this thread, we are doing research.