Hi @KarenC, I have a feeling you have the wrong theme version. If you go to the Foundation Theme page, you will notice the button that allows you to download the theme says 1.5.2, this theme will not work with the 1.4.5 stacks that you probably have installed. Under the button is a blue boxed area:
Click on the download it here link and install that version of the theme and the error will disappear.
Now, you could keep the theme and join the Stacks 3 Public Beta, which once installed, you will get the update to the Foundation stacks to 1.5.9 when you check for updates. Once those are installed, you will not get the error.
So you have a choice, update to Stacks 3 now (in beta) or wait for it to be released (time is unknown at this time, but close) and get the Stacks 2 theme.
Let me know how it goes.