Major problem with Safari..... and the spinning ball...
My Macbook Air works fine so long as I do not start Safari - the moment I do I get the spinning ball (in a multitude of programs, but mostly in Safari) and this condition does not go away until I reboot the machine (even if I close Safari down). On occasion I have had to reset the SMC to get the machine oeprating properly again. I have had this now for a couple of months (basically since upgrading to Snow Leopard) and I am certain it is Safari related. I have cleared caches, reset Safari, deleted Safari and then re-downloaded and installed; all to no avail. I am simply now living without Safari and having no problems - but this should not be necessary especially on a Mac machine!! BTW Firefox works flawlessly.
MacBook Air first edition, Mac OS X (10.6.3)