Ok, thanks again for your replies,
Nobody else had opened it, however one of my colleagues had tried to install the BETA version a week or so ago and it failed (!!), I believe this may have overwritten some .dll or install files but never fully completed the install.
I originally opened the project successfully (v2.0.6) --> did a 'save as' --> renamed the file (v2.0.7) --> then couldn't open the new file due to a database mismatch...
It also meant I couldn't uninstall / modify / repair the Visilogic software as the installer files were the wrong version and the PC threw