and the problem is fixed.
apt-get install openvas-menu
What has happened is that when you did the upgrade, you have managed to get stuck half way between v2.x and v3.x
FULL EXPLANATION FOR THOSE INTERESTED
When the packages were made for v3.x, the plugins package had to be modified to make it compatable with v3.x because as of v3.x they are not supplying an updated set of plugins and because of that they moved 4 files into a different package. This meant that for any install you would have to download ALL of the plugins from scratch via the internet. So to give everyone at least a base ammount of plugins (approx 12,000) without having internet available, I made the v2.x plugins package again just leaving out 4 files from it which are included as part of the openvas-scanner package (one of which happens to be openvas-nvt-sync). By doing this the compatibility of the plugins with v2.x was unfortunately broken, but as anyone updating the plugins package would also be updating to v3.x I didn't think this would be a problem (in hindsight perhaps I should have put in some protection against this, but then 20:20 hindsight is always perfect).
Well that's what happened, why it happened and how to fix it (hope it made some kind of sense).
Sorry for the error, it looks like I may have to go back into the package/s and add some rules to stop this happening again.