Well, that is weird!
When weve installed 1.15 it seems that sound and music was turned off by default. Every test to turn either music or sound on crashs the client!
Reproducable every time for every of our members: Start client, goto options, try to turn music/sound on, crash.
Edit: This fix brought the sound back but it seems no IC sounds: http://player.to/ic2_20111003_v115/soundsystem_update.zip
Edit2: Machine sounds needed a while but its there with that fix! Enjoy!