Johnny: see my above post.
I have a MX300 also and had the same problem with the sound cutting out after a second or two, it's definitely a IRQ conflict. Even after I had free IRQ's after switching to a standard PC I still had to switch slots until all the cards were happy. Now it works just fine. Now if only my new Viewsonic PF790 didn't have all this damn moire. Looks like it's going back