Got a response to this, and it has been sorted:
Apparently, the plugins that were appearing to malfunction require Aero settings on Windows 7 to be enabled:
I didn’t get this error message, but this appears to have been the issue.
Whenever I have set up Win7 machines, I have always tuned them for best performance i.e System Properties > Performance Options > Adjust for best performance.
This disables “Aero” automatically. In order to restore functionality, at a bare minimum you have to have “Enable desktop composition” and “Use visual styles on windows and buttons” checked.