Alright. Well, after basically trying everything above, I got it working!!! I guess some plugs can be fussier than others.
So, in summary, I did:
Deleted the folder in vstplugins and redid the unzip process,
Restarted OS and ran Sonar as Administrator,
In VST Settings, forced a rescan on existing plugins, then forced a rescan on failed plugins.
The VST scan cycled through all my plugins several times, hung on Drumatic once, which I forced closed and then suddenly after passing through the process again, scanned properly.
I have no idea exactly what in these steps did the trick, but thanks to the help, I was able to hit the magic combo I suppose. Now it works great.
I wouldn't normally fuss so much over a specific plugin, but it's for a collaborative track and I really wanted to get the synth working so I could tweak things and not have to go back and ask for the audio.
So, cheers everyone and thx so much for the help and your time.
Tom