Start up problem: iMac

Yesterday, I was using my computer when the power strip it was on was overloaded. It switched off. The strip is surge protected. When I attempted to start up my computer again it started having problems. Everything functioned correctly until I logged in. It would not load the menu bar, or the icons on my desktop. The dock appears, but when I click on an application I get nothing but the spinning wheel. I have restarted it many times, with little difference. I left in on overnight, and the menu bar finally loaded, but again, when I clicked on anything, all I got was the spinning wheel.

The computer was working perfectly prior to the power strip overload.

I would appreciate any advice.