Spinning Beach Ball in Safari, relentless, despite passing hardware diagnostics
My early 2008 24" iMac gets the spinning beach ball and stalls out, I use Safari constantly so that's where I'm noticing it the most. When I reboot the computer, it initially works, then after a few minutes it starts spinning again. Sometimes my pages load, sometimes not and then I have to close Safari and open it again to get it to work.
I installed Smart Utility And Smart Reporter, checked my harddrive with those programs, it passed all the tests. I run Onyx weekly. I check my activity monitor, I have plenty of harddrive space, my CPU usage is low, I don't have a lot of open programs, but I still get the beach ball. When I access the Force Close Applications, it shows Safari not responding. Sometimes my third party MailPlane will also show that it isn't responding,
I've read everything I can think of, can't figure it out.
I do have a replacement Seagate Barracuda 7200.14 (AF) 500 GB in this computer. I replaced the original harddrive two years ago. I also have 4GB of RAM, 2 GB in each slot. I thought perhaps I was having harddrive failure again, but every test I run says my harddrive is okay.
Any help would be appreciated.