Progress update:
I have put together my test program and posted the question on a couple of forums.
I have been experimenting with various file converter programs to see if I could produce .ogg files that consistantly have the load-problem, and I found a couple that do - "VLC Media Player" and "MP3 Converter Simple". Both of these programs have a lot of settings to choose from when saving the .ogg file, so I am going to try and play around with these settings to see if I can figure out what causes the j-ogg loader to choke. Hopefully that might help in tracking down the source of the problem. At the very least, it will provide a work-around until I can figure out what is causing the problem (changing the settings on the existing .ogg files to make them compatible with SoundSystem).
--UPDATE--
I have been playing around with converter settings, and I can not seem to find any discernable pattern. The settings in one converter will produce a file that can't be loaded, while the exact same settings in another converter will produce a file that works fine. The clicking problem also seems to be completely random from one converter to another.
I did however discover one important thing: very small .ogg files almost NEVER load properly, no matter what their settings are or which converter was used to create them. I'm pretty sure that is why your Login Sound.ogg file will not load.
So, until I figure this problem out, here are some work-arounds that you can use:
1) For the larger music sounds that you stream, until I get this problem fixed, just run your files through a converter which produces .ogg files that are compatible with SoundSystem. A simple freeware one that I like is called "Free Audio Converter", which you can download from
http://www.free-audio-editor.com/FreeAudioConverter.exe. It seems to do best when converting from .wav to .ogg, so I would recommend converting the original .ogg into a high-quality .wav, then convert that back into a .ogg with whatever compression level you want (otherwise it will sometimes add in small random clicks and scratches).
2) Use the .wav format for any small sound effects that you are not streaming. Note that the actual audio data itself is the same size whether you loaded it from a .wav or a .ogg, so unless you are streaming the audio, there is no advantage to using .ogg files over .wav files. Of course memory is often a concern for applets, so in order to avoid the memory required to compile your .wav files directly into the JAR, just pre-load their audio date from online URLs instead, by using the loadSound() method. Just make sure the filename you pass to SoundSystem begins with "http://" (that is how it knows to look online rather than inside the JAR). Hmm.. I just now realized that I never provided an unloadSound() interface method (I'm sure I did, but it must have disappeared somehow). Anyway ... I will correct that in the next release.
Sorry for all the .ogg problems. Hopefully this will be enough to at least get you up and running - I have no idea if I will be able to solve this. If I can't get j-ogg to work, I may have to end up looking for other alternative ogg libraries.