After upgrading to Yosemite a few days ago, Google Chrome started "breaking up" on screen. By that I mean, the screen became like a fast moving venetian blind, rolling up from bottom to top.My computer also slowed down considerably, so I did a clean reinstall of Yosemite. Things have improved and I am now using Safari rather than Chrome. However, when I went to the App Store today, the graphics at the top of the page started breaking up into a similar venetian blind rapid rolling. I have run Disk Utility and it says the hard drive is ok, but I suspect this old computer of mine might be on the way out!!! Any feedback or suggestions welcomed. PS: The problem is also happening with Airmail 2. Definitely something to do with the graphics display.