Maybe it has something to do with the preview options.. Rampreview always gives you sound after rendering, but hitting space bar (whatever that mode of preview is called) doesnt, scrolling through the timeline doesnt either. You can however, hold the control key (iirc) while scrolling, and then you'll hear stuttering sound. Hope that's what you mean.
Btw.. someone else tried AE CS3 preview yet?
Those shape layers are fun, so is the puppet tool.. But i think the only useful option for kara is 3d stuff, something bout extra 3d options.. rotating round a cilinder and stuff