Is "localStorage" in Firefox only working when the page is online?

So I'm toying around with HTML 5 and the localStorage and I'm noticing that my values only get stored when I run the page in Firefox on the local host (i.e. http://127.0.0.1:8000/test/index.html), but when I run the file locally (file:///C:/test/index.html) my values don't get stored. Safari 4 has no problems with both setups. So does anybody know if this is by design -> DOM Storage on the Mozilla Developer Center

(Firefox 2 permitted access to storage objects higher in the domain hierarchy than the current document. This is no longer allowed in Firefox 3, for security reasons. In addition, this proposed addition to HTML 5 has been removed from the HTML 5 specification in favor of localStorage, which is implemented in Firefox 3.5.)

Or if there is a workaround?
I wonder because offline storage that works only online sounds silly :P

If anybody wonders, the code is as easy as it gets:

function save()
{
 localStorage.setItem('foo','bar');
}

function load()
{
 var test = localStorage.getItem('foo');
 alert(test);
}