Firefox upgrade problems

[Ian Brooksbank]

This morning I was offered upgrades including an upgrade to Firefox, but 
when I tried to apply these I got two faults due to an apparent 
inability to overwrite two files :
var/lib/mozilla-firefox/extensions.d/00classic  and  
usr/lib/mozilla-firefox/components/libmozgnome.so

I tried several times to no avail, and even tried to uninstall firefox 
via package manager, but when I tried this it was offering also to 
remove the Ubuntu Desktop.  Although I did nothing that should affect it 
Firefox has stopped operating, and I seem to be stuck.  Can anyone 
advise me about this, I guess I'm not the only person with this problem??

Cheers

Ian