Outline boxes appearing wherever I click

I don't know how else to describe it. Write now, as I am writing this message for help, a black box appears around the window in which I am typing. When I clicked on the Subject box, it was highlighted by a black box.

I see the same thing happening on my desktop. If I click on my Hard Drive Icon, a black box appears around it.

I have tried to reset my permissions, but no luck in solving the problem.

ALSO, in my Apple Menu I have a "Restart" and a "Restart..." This is the same for Force Quit, Shut Down and Log Out.

This all happened when I was online with Safari 3.2.1 and my cat jumped onto my keyboard. I downloaded Mac 10.5.6 when I purchased it, so I don't have a startup disc for it.

Thanks in advance for any help.