Menu system breaks up in IE

I recently had to reinstall Austin Stacks GAA Club following hacking. All is OK except for in Internet Explorer wher the menu system and banner section at the top breaks up. This also happened a few years ago and I got a fix at that time but I can't remember what it was. I have tried to find a solution on the Template website (Joomlart) to no avail.
Here are screenshots from Firefox (correct) and IE8 (broken).

Can anybody please suggest a fix for IE8