Weird problem with Sonar Platinum (latest update), VEP6 and Kirk Hunter Concert Strings

Just a ping to see if anyone has encountered this and has an easy solution or work around.
 
The setup: Sonar sends the midi data over the network to another computer via VEP6. I'm using the Kirk Hunter Concert Strings Combo multi within Kontakt 5.5.2.880 on the slave computer. The KH CS multi contains four Kontakt instruments (one each for 1st violins, violas, cellos and basses). The Combo crossfades the various sections in order to allow a playable string orchestra across the keyboard.
 
The problem: The cello section becomes unresponsive after a few play-throughs. The basses, violas, and violins all continue to function correctly, you can even hear the crossfades from the sections adjacent to the cellos(where they overlap). The midi seems to be reaching VEP6 and Kontakt (it would have to be to trigger the crossfaded notes), it just doesn't produce any sound from the cellos. The easiest way I've seen to restore the cello instrument is to quit and reload the Sonar project (that is a pain!)
 
Any suggestions are appreciated.