Ok, deleted the test site and started over. Here's a step by step:
Action: Installed the QuickStart
Result: Site works on Chrome.
Result: In IE9 the S5 Accordion Menu on the homepage doesnt slide open when clicking the + .
Action: In "Template Manager", changed the background color to white
Result: In IE9 the S5 Tab Show extention doesn't display correctly (doesn't work at all).
So it has nothing to do with me updating the Joomla version or changing any content.
In IE9 the S5 Tab Show does work when you navigate to the S5 Tab Show info page from the mainmenu => Extentions
The S5 Accordion Menu partially works on any page (other than the home page). The menu slides open, but you can't close it. It only closes when you open another main menu item.
Here's the URL:
http://www.ethiopal.com/emanuel/btw, in IE9 using the compatibility option fixes the S5 Tab Show. But then other things go wrong so it's not an option.