Not sure why you're having issues with that. Odd.
Of course COD2 can be a pain to download mods, but I'm sure you've tried all the obvious methods - re-try, re-try, re-try, quit the game, open it, loop http://redirect.chi.gameservers.com/126.96.36.199_28960//main/P04.iwd
this is the file that you require, as you know, just drop in in your main dir
I really can't help you at all with any Mac specific information - sorry.
As for the sound issue you mentioned, again - odd. Works fine here.
You might have some conflicting files in your main folder. I would recommend dumping the lot. As we're not 100% convinced that's the issue, when I say dump it... I mean re-locate.
I created a screen grab of the only files you need to run MP COD2 inside your main DIR:
Just like I did, if you can on the mac arrange the files by Date, this will group all the files in the above together.
CUT every single file out of there that is not in the above and drop it in a new folder that is not within your COD DIR. So, just dump them in a new folder on your Desktop - or something.
Now join DB, maybe reconnect / close / exit a few times until you grab what you need and see if that solves any of your current quirks, if it does... just delete that folder on your desktop. IF it doesn't... then you can drop them back in to save you doing any further re-downloading.
It's worth a try. The aim here is to remove any junk you might have picked up along the way.
I believe we have a few mac players who are currently playing without any issue so I don't think it's mac specific anyhow.