Well I've solved my Firefox problems - I uninstalled it!
Seriously, after trying everything I could think of - including running every virus and spyware scanner known to man, disabling extensions, trying to run in safe mode, etc. etc. - and in the end in desperation ended up uninstalling all versions of FF from my machine and my profile. It didn't take too long to reinstall all my favourite extensions (also prompted me to ditch some I don't use) and as I use
Foxmarks I was able to simply synchronise from the bookmarks on the server. Seems my profile may have got corrupted somehow and that was causing these problems. No idea how, but the total reinstall seems to have cured the problem, so I'm once again a happy angel.
