Just to further elaborate/clarify.

I started a song file from a blank style. Filled all 7 available tracks with realtracks (no midi). I had the fiddle in question (#3094) in the bottom track on the mixer (labeled soloist). Any other instrument I loaded in the soloist (7th) track worked perfectly. I tried putting #3094 in all the other tracks (except the designated drum track) and it wouldn't work in any of them. Again, only in this particular song. When I created a brand new session, it loaded, generated and played perfectly.

Like I said, it's the oddest thing.