jb: Have you ever altered your read/write cache settings? I believe the default is 256 but I have mine set to 512 because of the large projects I do. Maybe yours is set to 128 perhaps? If so, check that out and try increasing it.
Screen set drop out: I get that in one project. The Cori Yarckin demo that Sonar gives us. It's the only project that does this to me...so it's definitely project dependent as far as the screen set change wreaking havoc. It matters not what box I run it on....and, it only does this in X2. The same project in X1, not a single drop out during a screen set. Not sure what the deal is there.
I read something about a floppy drive being in your bios being listed as "enabled" causing issues with screen sets. Those who have disabled it (due to not having floppy drives) have noticed screen set behavior is pefect. I don't have that option enabled in my bios and never have any screen set issues other than the one project.
But your audio drop out could just need a higher buffer in the I/O settings. See if it helps. It will also take the load off your hard drive for audio and will probably drop your usage down to like 10 % or lower. I run all mine at 512 in both of those boxes and don't check the box for read/write caching...just change the numerical value in both of those boxes to be the same. Good luck brother.
-Danny