Looks like I'm using FF 8.0 and it works fine.
I don't know anything about computers, but I think sometimes upgrades aren't quite compatible with some other program you might have- an antivirus program or a firewalll, or something of the sort. Not long ago I was using a version that was extremely slow on some sites. We got rid of an antivirus program (AVG I think?) and then it worked fine. Sometimes it seems to be process of elimination.
Karen
