I didn't have this problem with 2.7, but am seeing it in 3.0. I have a Sound Blaster in my Quicksilver. The volume is very low at default settings. I tried to go into pref to raise the gain to like 16.0, but the computer locks up when trying to do something with audio. If I put gain back to 0, no problem.
HiFi 16 bit stereo++ volume at +12 gain at +22.5db
It was working fine at first, then MorphOS would lock up tight as soon as something starts playing sound. I put volume and gain back down to 0 and the problem goes away. This is generic fresh MorphOS 3.0 install with Ultimate Pack 3.0 beta. I doubt Ultimate pack has anything to do with it but I will swap hard drives to one with MorphOS 3 with no Ultimate pack to see if I can recreate the problem.