Art Vista just stopped working!

After successfully completing a project a couple of weeks ago using one of Art Vista grands I started another yesterday (I use (Sonar PE 6.2.1, on an Intel dual core). The plug instantiated normaly, I selected a piano and recorded a midi track. However on playback no sound was heard and I then also got no sound when triggering notes on the GUI with my mouse. No matter what I tried (and either DXi or VST) I could not get playback. I uninstalled AV, cleaned the registry and reinstalled and updated. Still no joy. Anybody seen this? Is there a solution? Or suggested paths to take? Thanks for any info anyone can provide. I really need this package to work again.