In my experience the problem is the Click-To-Flash plugin/extension. I was having constant beachballs switching between tabs, always getting the Force Reload drop down alert, pages never loading, or having several tabs open and then when I switched back to another page it would be blank and have to reload which would take forever.
I originally just turned off Click to Flash in my extensions panel but it had no effect. Then I turned off all extensiosn and it still didn't help. Finally I just hit the uninstall button and the problem went away immediately and has not returned.
I can't say for sure if this is your problem, but if you have Click to Flash installed I would suggest removing it and seeing if that helps.