Hi Biggles78. I'm using Firefox 8.0. You'll see, two or three posts ago that I got it installed on my admin. account once I'd run Revo Uninstaller to cut out the older version. Revo uses, where available, the program's own uninstaller then gets stuck in with its own stuff to root out any odd scraps of program and related stuff which remains. I've used it a few times and it has worked well - just as efficient, in its own way, as Crap Cleaner and others.
What surprised me was the slightly odd process I had to go through to get FF to recognise that I had indeed already replaced the out of date version, which it had disabled on its own sayso, and so lift its ban. I'd have thought that it should have been programmed to recognise the appearance of the new up to date version automatically - even if, perhaps, only one encouraged by closing and restarting FF or rebooting the whole computer - both of which I tried a couple of times - but no. I had to delve into some deeper register of plug-ins and delete all of it (and therefore its registry of all of the other plug-ins as well). Restarting FF then prompted it to scan what was there and create a new registry (my layman's talk) and then all was well. It seems to me that FF could have done that before I had to interfere with its plug-in registry. It seemed just a little unnecessarily clumsy - maybe they'll read this and fix it, after all I can't be the only one who has been frustrated by the failing and everybody significant reads PPRuNe, don't they?.