I wonder if this happen because the rapid switching of sounds that you was doing. Never have happen to me.

I will like to know how the Audya switch sounds from memory. In computers when a program or process is running in memory and is no active anymore is keep in memory as long there is any available; if no is "swaped" to disk. This create a lot of crashed servers in computer world.
The Audya does no have a lot of memory; maybe the issue that you saw was because the switching between disk and memory.
In that respect I think that the Audya5 is going to have an advantage (more memory) over the original audya. It will be nice if Ketron can offer an expansion memory board for the original Audya.