I had a flawless install of Panther, but I went againstt the grain and did a basic upgrade. Everything was just peachy until a couple weeks ago, when Safari began to slow down big time. It got to the point where 10 minutes after opening Safari, if I was on a busy website, I would get the spinning beach ball every time I clicked on a link.
I tried all the usual stuff, with no luck. Finally, I decided to try logging in as Root, and see how Safari behaved, and to my surprise, it was awesome! It was quick and snappy again, and a pleasure to use. In fact, I stayed logged in as Root for several hours so that I could get some admin stuff done at my website, and not go crazy with delays.
I figured out which files were unique to each user as far as Safari is concerned, logged back in as me, and moved them to my desktop. I then restarted Safari, and it was great again. It has been ever since.
The point I am trying to make is to try logging in as Root and see if the problems you are having still exist. I found this made the diagnosis much easier.
Take care,
~Chris