I am using an imac G5 Intel. I had just installed a new 1GB memory card. While checking that it had been recognized, I hit the scroll button on top of the mouse. The display started zooming in until the entire screen only displays a few characters. I ran a test using the startup disk & everything checked ok. I have started, restarted, etc. with no improvement. Surely there is a simple solution to restoring the display to normal. Please help!!