Somehow, all the Plug-in settings against my profile had been reset to 'no plug-ins'. I'm fairly certain I didn't do this...
All seems to be restored now though...
Quite a while ago this happened for my profile quite a few times. Then it just stopped.
I suppose it must've been a 'glitch' of some sort, maybe with my web browser ('cos nobody else had the same problem at the time).
K x